I just read this thread today...interesting. In my experience, either a back fall or a forward roll, or a breakfall could be done. One experience from my journal:
Had one really perfect tenshinage during randori…uke did this wonderfull high flying ukemi as I entered strongly…probably the closest I'll ever get to doing anything like Utada sensei does. Instead of just turning palm down against the wrist for the top hand, I then moved to a soft but firm atemi to the side of the neck while maintaining connection with both hands. Uke rotated all the way around the bottom hand like it was a pivot point, going completely over the top. WOW. It'll never happen like that again…zanshin was a kick!
I asked my uke afterward if it was my waza that produced the breakfall, or if he was just being nice. He said that since I was entering so strongly, he really didn't have a choice. FWIW.
I should also note that I have done iriminage in a similar way...but it makes me nervous sometimes...one time uke's neck made a series of cracks as I threw him... The next time I did a similar throw, I controlled uke to 'force' the back throw...he was so busy trying to do a flying front fall, I just stopped and didn't throw. Uke wasn't very happy with me...