The value 64 is a BSC limitation (at least for 9120 G2 BSC, i don’t know for the new 9130 Mx BSC)
An incoming HO request is not put in a queue, the TCH is either available or not at the time the request is received by the RAM (resource alloc management function in BSC).
The queue is only available for call setup (= normal assignment).
If you want to book some TCH for incoming HO, you can do it. There are two parameters (or three?) to do so, per cell. I let you find them out 🙂
Then I can explain how they work (i need my document to remember.. will get it on monday)