It's certainly confusing as most Tascam interfaces include  "Cubase DAW " which was how I got my copy of Cubase 5LE. 
 
Here's some examples I just grabed from the Sweetwater web store: 
 
Confirmed operation with major DAW software, including Sonar X3, ProTools, Cubase, and Live
Includes DAW software
The US-2x2 comes with Cubase LE. A feature-rich recording software for musician, Cubase LE provides a cutting-edge music production studio, giving users what they need to get started creating music on your computer.
 
 In this one for the iXR 2 there's a hint at why they are choosing Cubase over Sonar.. do you get it?

• Includes Steinberg Cubasis LE for iOS and Cubase LE for Mac/PC
• Made for iPad Apple certification

It's why there was an attempt to port Sonar over to Mac.
My wandering mind came up with this possible situation: 
Tascam has always included Cubase and has that set up nicley with Yamaha/Stienberg.  Gibson buys Cakewalk then Tascam so tells them to include Sonar with their interfaces, Tascam replies- Sonar is not cross platform and the majority of our customers use Mac so sorry, we will continue include Cubase because we don't want problems from our customers. Gibson tells Cakewalk to make it Cross platform or hit the road, Gibson eventually scraps Sonar because the plan to port over failed.  

Cactus Music
It's certainly confusing as most Tascam interfaces include  "Cubase DAW " which was how I got my copy of Cubase 5LE. 
 
Here's some examples I just grabed from the Sweetwater web store: 
 
Confirmed operation with major DAW software, including Sonar X3, ProTools, Cubase, and Live
Includes DAW software
The US-2x2 comes with Cubase LE. A feature-rich recording software for musician, Cubase LE provides a cutting-edge music production studio, giving users what they need to get started creating music on your computer.
 
 In this one for the iXR 2 there's a hint at why they are choosing Cubase over Sonar.. do you get it?

• Includes Steinberg Cubasis LE for iOS and Cubase LE for Mac/PC
• Made for iPad Apple certification

It's why there was an attempt to port Sonar over to Mac.
My wandering mind came up with this possible situation: 
Tascam has always included Cubase and has that set up nicley with Yamaha/Stienberg.  Gibson buys Cakewalk then Tascam so tells them to include Sonar with their interfaces, Tascam replies- Sonar is not cross platform and the majority of our customers use Mac so sorry, we will continue include Cubase because we don't want problems from our customers. Gibson tells Cakewalk to make it Cross platform or hit the road, Gibson eventually scraps Sonar because the plan to port over failed.  

ahh yes,  this does sound like at least one part of the puzzle. if not the whole.
 

"Onkyo continues to created award winning products..."

That Tascam announcement is three months before the Cakewalk closedown announcement. There's no reason to think that Sonar is alive and well anywhere. 

Track Factory package with Sonar is still listed on the TASCAM website:
 
http://www.tascam.com/pro.ct/trackfactory_project/

What is so surprising about Tascam still including Sonar Pro with the Intel NUC PC?
It works, so there is no reason to scrap it.

I think the issue is many. It is not supported. I don't know if you can newly license it. I do think this is kinda a cluster of it isn't going to light back up in some new form.

probably a stock internal photo that was included in the promo campaign months ago and no one cared enough to swap the photo out 

Cactus Music
Tascam has always included Cubase and has that set up nicley with Yamaha/Stienberg.  Gibson buys Cakewalk then Tascam so tells them to include Sonar with their interfaces, Tascam replies- Sonar is not cross platform and the majority of our customers use Mac so sorry, we will continue include Cubase because we don't want problems from our customers. Gibson tells Cakewalk to make it Cross platform or hit the road, Gibson eventually scraps Sonar because the plan to port over failed.  

No, I was there. TASCAM paid a license fee for Cubase. The fee for SONAR was less. I engineered a deal where a light version of Live was included for the Mac users, and SONAR for the Windows users. This still ended up being more cost-effective than licensing Cubase. AFAIK the interfaces shipped with those products up until Cakewalk was shuttered.
 
My argument for Live was that on the Mac, GarageBand and Logic predominated so Ableton would offer more value to customers because it was something different.
 
My initial proposal was including cross-platform Cakewalk products like Rapture Pro and the cross-platform plug-ins for the Mac. I thought this could benefit all users, including ones who had already committed to a DAW. That proposal was rejected; I'm not sure why.
 
In any case Gibson was not dictatorial about creating a Mac version to benefit TASCAM.

Some mics i bought had 8.5 LE,a very good n
Cool example of cakewalks daw,but pentium III Windows XP machine(i was given due to it's impediments),that i ordered it with would not install it,though not knowing computer(S)much at
all,i still hahaheheh registered the almost empty folder-THE ONLY thing installed,ALBERTON was EXACTLY The same result from an AUDIO MAG's
cover dvd,and a few years ago I GOT CUBASE LE 6 with the N.I.KA6 usb audio interface(AND I'VE LOST THE CD ROM?DVD + - ROM whatever,)and
liken elicenser steinberg to iLOK especially with THAT proPROaudioAUDIO forum GS,or GEARSZ or,um yep a few folks posted in the sub forum(wt? sub forum is like metals too many genres styles i think)
grindcore,thrash,death,heavy,glam,hair,NWOBHM...genres in hard rock(not into that crappy word) for a style,or a yeah ok genre so created when ?
1974 when it supposedly became an *actual genre* or *style*,by,from music journalists-you guys in THAT job if you're lucky,and talented as a FB
friend is-best AC / DC book easily for me,i've read a few,not more, so if you can read writing,AC / DC book Maximum Rock & Roll about and of the
whole band-by 'Murray Engleheart' plus Arnaud Durieux(mines lent atm so a little stolen yeah?- 
o'heredear) so Did we miss this or did Tascam-i loved my old 244 portastudio,so things change,and get fixed,and explained before my 10k from late
2010'ish,and more ridiculous demands from hmmm hlthdept dr's NO lava till Hawaii!
THANK ALL OF YOU for being!
THANK YOU ALL huge big awe inspiringly if y'all can be tolerant of this so too!
being my best to be humble 
bob