This is an old post, but I wanted to share my (current) experience today booking Orbitz.
I booked my tickets through them fully expecting to get my Disney ticket confirmation number. Turns out, that will be true...but within 5 business days.
I used paypal as well, which is linked to my bank account, but I would have happily used a credit card if I had the opportunity to obtain my Confirmation number now so I could plug it into MDE account.
So I'll have to sit here and wait, possibly losing an opportunity to select FP+ before they are sold out.
But to answer the question, for anyone else curious, yes, you CAN link your tickets to FP+ and use them just like any other WDW 3rd party tickets.
Also...you can't earn "Orbucks", Orbitz rewards program, buying tickets from their website unfortunately, but you can earn Ebates rewards.