When you import a MIDI file (which I *believe* is the functionality of drag/drop from the browser), it strips tempo information, so will match the project bar-for-bar with the original recording (just the tempos may be different). If the drag/drop has issues (I checked X3, and seems to be fine), importing MIDI on a track definitely works.
 
Flip side is opening a MIDI file will retain tempo information (if present), but this is not what you are trying to do.

Thanks mettelus!  
 
BTW I am also kofgadol ... due to a now-rectified tangle up with profiles I was unable to log in as lingyai, so used kofgadol temporarily

Not a problem. FYI (for the future), if this is a critical workflow that you will use often, the newest version of SONAR includes the ability to slip-stretch MIDI (under MIDI enhancements in this link). This removes the "Start a new project" step (which personally bothers me, as I have things I do that still require this is the new SONAR), and will simplify your workflow to this:

1. Select the tracks you wish to play accompaniment to (slow down).
2. Track View menu -> Bounce to Tracks (new track).
3. Solo that new track, Slip Stretch audio in that track to taste (and bounce to clip(s) if desired for audio quality).
4. Record MIDI track.
5. Mute the bounced audio track.
6. Slide the MIDI track to the appropriate start time to the original piece.
7. Slip-stretch the MIDI to proper size (the part X3 lacks for you to simply do this).

If you run low on CPU power or get latency issues, archiving that bounced track (when not in use), will actually remove it from CPU consumption if you choose not to delete it because you may use it later. Similarly, a soft synth with heavy CPU overhead can be frozen to render it as an audio track (and can be unfrozen to make changes to as necessary).

I have a simple solution to this problem . 
I just make sure there is enough midi parts to play along with and mute all audio. 
It may involve creating some simple bass and piano tracks say if your song has real bass. 
And I guess now a days you could even use the real bass track to make a midi track.