Imported MIDI will take on the tempo of the project into which it's imported. But if it's on the beat, that would be odd given the audio from which it was extracted was not synced to the timeline. If you
open the MIDI file from SONAR rather than importing it, the tempo(s) of the original project will come with it, and it should play with the same timing as that audio. But given that it didn't do that in the original project, I don't know what you'll get. Something isn't adding up, but without seeing the actual project firsthand, it's hard to say what might be going on.
Incidentally, the Timebase setting only affects what happens to the
start time of a clip when you change the tempo. By default, both audio and MIDI clips will retain their MBT start times, staying aligned with the timeline when you change the project tempo. If you switch to Absolute, nothing will happen until you change the tempo, and then clips will appear to move relative to the timeline as they maintain their absolute start times. But with either setting, the
length of a conventional audio clip (i.e. not Groove-clipped or Audiosnapped) always follows absolute time, and the length of a MIDI clip always follows MBT time.