I may be wrong but....
Pro IP's have been trained in 727 stuff and just need IOE. Corp types may be senior but have to complete full 8 weeks of training prior to IOE.
Note: Seniority determined by SSN, not date of hire or age. So, you may have a corporate guy number 1 in class, pro IP numbers 2 and 3, corp number 4, etc etc. I would expect those pro IP guys (especially if they are 727 trainers) to go straight to line and IOE.
Been wrong before...will be again...