PGSM is the basic GSM band, everyone MS in the world can support this band 🙂
The problem is if your nw uses the G1 band, which is only available to EGSM mobiles. In such case, you must fine-tune your freq plan and your algorithms so that PGSM MS are not left behind, and are still able to connect to your network too.
In your case, PGSM only, the EGSM RR ALLOC parameter is useless. But I forgot the exact function of thie parameter.. so if you just post its definition then i might be able to help more.