I mean...how do you even extract a MIDI file out of SPlat, since it seems embedded in the session file?
I imagine audio files wouldn't be too much an issue, (but what's the easiest way??) but those pesky MIDI tracks.

It has been awhile but I think with Sonar you export the midi tracks to get a midi file. It will ask if you want type 0 or type 1.
The audio files should be bounced to clip so that there are no fragments.
If the file doesn't start at location 0, slip edit it to location 0 then bounce to clip again.
 
Now you can import the wave files and midi files into your new daw.
 

Yeah...I dragged them into the explorer tree after bouncing them to clips and that did it.  Even could rename at that point too.
Now... exporting the tempo map!!!
I'm really actually getting to like Studio One...probably because it's something new.  
But I've duplicated sessions and that's a huge plus.  My soft synths I need to see what I've changed in the paremeters....but otherwise.... all working great.

Best part...I've YET TO CRASH

I forget now if SONAR exports the tempo map with MIDI, but it should.

Dragging in a tempo map (with MIDI) is as simple as dragging a MIDI file onto the start page for a new project.

I have had S1P a year and got it to seize once on boot due to a sample rate mismatch (it popped up an error window detailing what to do), but other than that I haven't gotten it to crash yet.