A vocalist I'm working with has ProTools and we are collaborating on a song together.  I'm not at all familiar with that software, and she is kind of a newbie with it as well. 
If I send her a mixed down version of a song of all the instruments, like in a wav file, so she can import and add one or more vocal tracks in her ProTools, what's the best way for her to send it back to me so that I get the original instrument track and new vocal tracks all aligned.

Is there an export format on ProTools that I can import into Sonar that will create a package of all the individual tracks synced up?  If not, what's the best way to do something like this? 

The last time we worked on a song together, she just sent me the vocal tracks, and I had a hard time syncing up the vocals to the rest of the instrument tracks. She had several vocal tracks, including different takes, as well as harmony tracks. Thanks for any suggestions!

I have a similar question. I's love to be able to move take lanes from ProTools to Sonar.

Sonar supports OMF files.
This is something I would look in to if your wanting to collaborate with others using different DAWs and especially Pro tools.
http://www.cakewalk.com/Support/Knowledge-Base/2007013037/Importing-OMF-files-into-SONAR-2-1

I have been porting files back and forth from Ptools and Sonar for about a year now.  I have them both on my computer.  My clients send me AAF files I open in protools ...export an OMF so I can work in Sonar.  Then send the mix back in protools.  The issue I run into is clips overlapping.  So when I'm done in Sonar I "bounce to clips" every clip.  It finalizes any fades.  If any clips overhang Protools will not see either clip on the timeline or create another track.
 
So Freeze all your midi instruments,  "bounce to clip" any clips, then export an OMF.    You need to check "Embed Audio within OMF " and  " Split stereo tracks Into Duo Mono" when creating an OMF from Sonar so it will work in ptools.
 
You might want to "remove all silence"  to make your OMF file smaller.  Dont' use the default setting .. I use -93db to make sure i get good fade ins and outs of string parts,
 
Good Luck and have fun.

Thanks guys..  It's one of the few functions of Sonar that I'm unfamiliar with, so I appreciate the advice.

Yes I`ve doing it as  Jimbo 88  said ,exactly,cause I have to work with both Platinium and Pro Tools all the Time.
Peace

I do pretty much the same as jimbo88 when working between PT12 and Sonar.