Hi Safar,
I mentioned B-PDCH because I was trying to emphasize the fact that an FPDCH/SPDCH can be any kind of PDCH (E-, G- or B-BPDCH).
Any idle TCH can be used as a PDCH, and the PDCH can be an E-PDCH, G-PDCH or B-PDCH. The only limit to the number of PDCHs you can have in a cell is the number of idle TCHs in the cell. If you have configured 30 EDGE timeslots( E-PDCHs), then any other PDCH which is allocated above 30 will be a B-PDCH. I hope this answers your question.
Regards,
SHELDON