2g, 2.5g and 3g traffic

Dear all,

I have GSM and GPRS traffic data from ericsson system and want to use them for 3g traffic forecast. There has some question while I am doing it.
1. I can get the busy hour Mean hold time by do huge statistics for sites of BSC or MSC. How to get the BHCA by using the real traffic counters?
2. I need creat traffic raster in planning tool. The traffic is concerning the weight of clutters, vectors and polygons. Is any way to get more accuracy weight of them?
3. We know that Ericsson GPRS R8 only supports CS1 with 9.05kbps and CS2 with 13.4kbps. CS1 is mandatory for BSS and CS1 to 4 is for MS. Ericsson traffic formula is only considering CS2:
RBCDL(or RBCUL)*/50/3600 Erlang or
RBCDL(or RBCUL)*12/50/3600 k bit/s.
why they use 12kbps instead of 9.05 or 13.4 for UL and DL?
4.How to get mean busy hour capacity for GPRS per subscriber by using the real ericsson counters?
5. Any advise convert 2g and 2.5 g traffic to 3g traffic?

Thanks a lot.
Charley