Slim,
Yes : no timeslot to be allocated for the incoming HO. Usually it means that there are no free TCH available, but some (rare) cases where there are TCH left, but none of them can match the capability of the MS (for example : MS is only FULL RATE and the only TCH available are HALF RATE)
inter-BSC case : yes, the external target is congested after T QHO has expired. During 6 seconds, the “serving” BSC will not try to HO to another cell. It still hopes that the external target is available.
Cheers,
pix