I am in the same boat, I went through a rigorous interview process and just signed an offer letter. This is a full time position and my employer will file for GTS to expedite the process. I scheduled a 30 minute session with an immigration consultant to understand the GTS process and this is what he mentioned;
The GTS is reviewed carefully and has a high denial rate.
If your company has had a favorable GTS application in the past, it should be an easier process for them and CIC.
The GTS LMIA should take 2-3 weeks to get approved.
Once you get the approval you CAN update your existing (or new) PR profile and claim the points
You will need the original LMIA for the PR filing
I am stuck at 437 with my PR and will go down to 432 next week, counting on the GTS to go through.