Yes, GPRS is very flexible, and you can always config the system as you preferred. When MS power on, it first camps on BCCH, and listens to SI13 message. The SI13 message will indicate if the cell supports PBCCH or not. If there is PBCCH in a cell, and if in Network Operation Mode I, a GPRS-MS will monitor PBCCH (also for GSM information) instead of BCCH. If this cell doest not provide PBCCH, the MS will continue monitor BCCH for GSM (SIxx) and GPRS service (SI13).
If you want more information, plz do not hesitate contact me at vndnguyen@hopthu.com.
Brgds