the LU follow-on is when the MS performs a LU and asks for a TCH at the same time : during the sddch phase, the location update is performed and then the BSC allocates a TCH to the MS, for the call.
Basically, the MS wants to do a LU and then a call. I don’t know when this ever happen, i can’t find an example… if you have any idea, you’re welcome to share.
In terms of counters : how many MC02d and MC02a are counted at busy hour ? MC02d should be very low.