This has been the bane of my existence, but I came across a post that showed how to do it. I am capturing it here for any poor lost intrepid souls.
If you have a tempo map that you spent hours, yea, days to perfect, you can move it to a new project. I wanted to do this so that I could update an old project to a new template. Here’s what I found out:
Load the MIDI file containing your source tempo map into Sonar as a new project. Then open up the tempo map to make sure it’s actually in there.
Then Select All and then hit ALT-CTRL-C (Copy Special) and make sure that only “tempo changes” is ticked. Hit OK. Now the clipboard should now contain the tempo map
Then open up the project that you wish to merge this tempo map with. Move the NOW to the start of the project. Hit ALT-CTRL-V (Paste Special). Make sure that the Tempo Changes is the only event type ticked. (All other event types should be greyed out as the clipboard should only contain tempo change events)
Note, you may need to open up the tempo view before doing the Paste to make sure there are no existing tempo changes that would confuse the project.
Open up the tempo view and your tempo map should be present there as pasted.