Found this Video showing how to do it in Reaper.

 
So it seems that SONAR sees Rearoute (if I disable my RME ASIO devices). Seems like a simpler way to get that Mixbus Sound without exports/imports.
 
One drawback, ReaRoute only has 16 "ports" and so from SONAR one must be judicious in internal routing how you were going to use SONAR routed into Mixbus. Think of SONAR's output to Mixbus as a 16 track tape machine.
 
1st Disclaimer: I have not entirely tried it ye.
 
2nd Disclaimer: You should own Reaper to be able to install ReaRoute but far be it from me to mention that you can install a demo of Reaper that never expires and I believe you will get ReaRoute that way.
 

I managed to realtime route Sonar buses into Mixbus last spring just using my MOTU interface (there must be some posts in a similar thread where Kenny pointed me to Mac video that showed something similar and got me started ...)

Anyway, I did not follow up further, mostly for limited time, but I now believe there are too many drawbacks if you think it further ...

This way you could use Mixbus as a summing engine but as soon as you want more than a static set of summing settings, it'll become hassle. You would have to enable some sync (possibly via some virtual MIDI port) and then record all automation in Mixbus in real-time as you would not have clips to guide you ... if all successful, you probably cannot just bounce but would have to figure out a way to record your mix ...

Overall more complicated than exporting all from Sonar and importing again Mixbus IMHO

Rob,
 
Thanks for the mention on using hardware. I would think I could do the same with my RME UFX.
 
Thus far I only write automation in Mixbus in real time, so that's not a deal beaker for me. In fact it's like I get to keep the same feature I already use.
 
Since I pretty much try to have about 6-8 prefinal buses, prior to the 2-bus, in SONAR; this pretty much makes sense to me as a method to try out.
 
The video does show how to get a "mix" out of Mixbus into a SONAR track, FWIW.

Let me know how it goes if you seriously give it a try. Might hook it up myself for another trial ... would need to get the control surface setup sorted in Mixbus first as I wouldn't want to do real-time automation with the mouse...

Rob[atSound-Rehab]
Let me know how it goes if you seriously give it a try. Might hook it up myself for another trial ... would need to get the control surface setup sorted in Mixbus first as I wouldn't want to do real-time automation with the mouse...

Even though I did not try it I was doing a mental exercise on it yesterday.
 
How on earth did I think I could write real time automation in Mixbus if it's not really playing (since it's sans clips)?
 
DOH!