This just in from the Kitten Farm east as Katherine and the boys negotiate on their travel conditions:
No collars for the boys. Whitey's escape time was about 10 minutes. It would be faster in a carrier, since he couldn't spend half the time running away from it. He also hid the collar. (Probably behind the tall bookshelf he sleeps on.)
Billy didn't escape, mostly because he may have been afraid to move for fear the collar would pounce on him.
I find the learning to hide the collar since we last attempted to give them collars a nice touch.