Teal, you can extract tempo using various tools. My preferred method, as I mentioned above, is to tap along with the rhythm and extract it from the midi data.
 
You can extract it from audio data too, but you are depending on it to ignore a lot of variation you can clean up by tapping along with the song. You can also set ever down beat manually if you want. So, off hand, I'm thinking of 3 methods for extracting meter from work recorded without a click track.
 

Teal

Anderton

puffer
...download the demo and take a good look at the aforementioned "Tempo View". This is the same tempo view that's been around since SONAR 2. For me, it's a little long in the tooth and a PIT-ever lovin'-A to edit. It's a pen tool rather than a node/spline automation system. As also mention, there is a history of VSTs not playing nicely with the "tempo view". It's a real weakness of Sonar--in the opinion of a small number of users I guess.

I find it easier to click where I want the tempo change, and go Project > Insert Tempo. You can specify tempo down to hundredths of a BPM, as well as the precise spot where the tempo should change. You can also specify if you want to change previous tempos or not.
 
If you then want to create an ultra-smooth tempo change, you can bounce over to tempo view and use the pencil.

Do you have to put in each tempo change manually?  Samplitude has a remix agent that can analyze audio composition and insert markers for each bar/beat.  It automatically calculates the tempo changes so all you have to do is run the agent, listen and nudge some of he markers for accuracy and you are done.  

I'm not talking about analysis of existing audio, but creating tempo changes to add interest to a song, e.g., pulling back a bit before the Big Chorus and upping the tempo a tad during the lead guitar solo...that sort of thing.

Craig, Every time I post about this issue someone "suggests" that, kinda missing the point of what I'm talking about.
 
No, I get it. If you want to have a simple tempo change up or down a few or more bpm just insert a new tempo at that point in the song. Works for me, works for you, no if, and, or but. Though, as you know, in scoring and orchestration, tempo can ramp up and down, often in very tight amounts of time; when you get into the editing of those ramps you enter some frustrating areas.
 
Example: You're scoring a video. Say a 3 to 5 minute --the director's not sure-- fashion video, showcasing some jewelry designs. You start working with a rough cut, and there are 4 or 5 "sections" where the video demands separate but related movements. There are transitions you build with, say, a string crescendo while the tempos shifts from 79bpm to 103bpm over 6 bars. To do this you drop a couple of markers and the corresponding tempos, then in "tempo view" you draw an upward line between the 2 markers. Being careful, even with this, because there is no "tempo snap" on the tool, so unless you aim perfectly it's easy to wind up with weird tempo fractions (e.g. 102.85bpm). Anyway, you do more work on your score. 2 weeks later you get a new cut, with several seconds, frames shaved off this transition. So you now have 4.5 bars to land on the new tempo, which itself needs to now be 100bpm to match other cuts.
 
I'm not saying you can't do this with the current method (in as much as something with a 10-year old GUI is able to be current), I'm just saying it's fiddly and annoying. It always has been; more so now that the nodes & splines of automation lanes are so sophisticated. But apparently this is my own little axe to grind with SONAR.
 
That said, I don't think this is precisely what the OP is asking. I believe that questions was, can someone record a track from which SONAR can than extract tempo information from. To which I believe the answer is yes, using audio snap. I think there was, is a tutorial video floating around on how to do this. I'm just saying, if you want to edit that tempo in any sort of less-than-straight forward manor, be aware of what lies ahead.
 
Cheers for the info RE: the VSTs.

puffer
I'm not saying you can't do this with the current method (in as much as something with a 10-year old GUI is able to be current), I'm just saying it's fiddly and annoying. It always has been; more so now that the nodes & splines of automation lanes are so sophisticated. But apparently this is my own little axe to grind with SONAR.
 

A tempo map with nodes and splines like the automation lane would be a nice improvment. Did you submit a feature request?

Teal
1) Does X3 have anything like a "tempo track" or ability to change the tempo over time to match acoustic performances that were not recorded against a metronome? 

 
There is a "Fit to Improvisation" feature.  It's not easy or efficient to use, but it does produce good results if you are prepared to spend some time with it.

You can "draw" in the tempo view (graphical representation of tempo vs time) as an easier way to insert events. However, I'm not sure if drawing in the tempo map is the right way to sync events. The granularity of the inserted events makes a big difference in the elapsed time from beat to beat. So doing it that way is not really good for syncing. Really, when scoring, timing is more to the point than the "gradualness" of tempo change.

puffer
Example: You're scoring a video. Say a 3 to 5 minute --the director's not sure-- fashion video, showcasing some jewelry designs. You start working with a rough cut, and there are 4 or 5 "sections" where the video demands separate but related movements. There are transitions you build with, say, a string crescendo while the tempos shifts from 79bpm to 103bpm over 6 bars...

Agreed. It's difficult for Sonar to accommodate those types of tempo changes, especially when they cut a few frames from a video where you've already done the audio, and you're stuck with trying to compensate.