It is definitely working with the latest ProTools versions. We have done that several times, exporting a timeline in segments and rejoining them in ProTools. But we have a very experienced ProTools operator in the audio studio, and I don´t know how much hidden "magic" he has to do to get this together.
Best thing you can do is to create a small timeline but with many tracks (maybe using only one audio media file placed various times on these tracks) and do a test-run. If the original audio clip is short enough you maybe can FTP or mail it and the timeline to the studio doing the conversion to you, so it would not take too much time for you and them. Then give that to your audio studio and see if they can do something with that. And have a look if all needed informations are carried over.
If you want I can do the test for you. Just
mail me a sit file with a timeline and the associated audio clip and you will get back an OMF. This would at least test if your sound studio can use Media 100 i OMFs.