I was working with a project that had all the tracks and I wanted to change the drum track.  No biggie... however, the original was recorded using the drummers sense of timing which resulted in a slightly varying tempo throughout the song.  Apart from painstakingly going through the project and manually inserting tempo changes where needed, is there an automated way of doing this?

Try reading up on the "Fit To Improvisation" feature. It's not necessarily easy or straightforward to use, but it does what you are asking.
 

Thanks Kev, will check it out

An Asimov fan, huh (assuming that's not your real name)?
 

Hehe, you know your Sci Fi
Should be one L not two but a jittery keypress evaded my detection until I couldn't sign in on the chosen name
 
Ok, Fit to Improvisation didn't want to touch an audio track.  I think it is for midi.
 
What I ended up doing was still painstakingly going through the whole song making tempo changes where appropriate but it was made easier by using "Project - Set Measure/Beat at Now" which did a much better job at determining the new tempo.  It was a pain in the fundamental harmonic to do this with a continuously varying tempo but it was easier than trying to guess the new tempo.

EllijahBaley
Ok, Fit to Improvisation didn't want to touch an audio track.  I think it is for midi.

It's for audio really. Midi clips always follow the project's tempo anyway.

The way I would use it is to create a midi track next to (above or below) the drum track. Add a (short, e.g. 16th) note on every beat. Using the inline PRV, and using the drum audio tracks peaks as a visual guide, adjust the timing of each note on the midi track (with snap turned off of course). When you believe you have matched the timing of every beat, select the midi track and apply "Fit To Improvisation". This will automatically insert appropriate tempo changes at every beat.

Worth mentioning is you don't really need a actual tempo for a song unless your planning on recording more midi instruments, like piano that you wish to quantize. 
 
But what Kev has recommended is what I have done,,, once, it was a lot of work. After that I just use my ears and edit any bad piano timing issues if I hear them, faster. 
I find if a song has a wanderning tempo , best to not try and fight it into a timing box, just let it roll..

Yes I was planning on using Sessiondrummer or Addictive Drums to change that track so tempo changes were required. What I did has worked well but it took some time. I appreciate the comments, thank you

Kev999

EllijahBaley
Ok, Fit to Improvisation didn't want to touch an audio track.  I think it is for midi.

It's for audio really. Midi clips always follow the project's tempo anyway.

Yes they do, but I had imported the audio tracks and was trying to setup the project tempo to match so that any midi I created would be in time. When I tried Fit to Improv it just ignored me so I guess I need to read up on that a little more.

Just so you know, If your just doing drum replacement, you don't need to sync to tempo. Audio snap ( now melodyn) will create midi events for each drum part. One of the beauties of drum replacement is you can mix in the original drums as well, best of both worlds. To me this is one of the best ways to get a smoking drum track. I mostly replace the kick all the time. Toms are a bit tricky depending on the mike set up because of leakage. 
I now will be using triggers next time I use real drums. 
 
You can also make minor changes to any hits that were way off time by dragging the midi note.. but you'll have to mute the original for that hit.