it is disgusting to see that nobody is interested in such an important & interesting topic. by the way i got my information. the gsm specified limitation is 64 neighbors but no mobile can scan for more than 32 neighbors. so this is the practicle limit.
can u tell why the limitation of 64 neighbors keeping in view the sys info messages. the information about neighbors comes in sys info 2 in idle mode & sys info 5 in dedicated mode. now this information is in the form of a bitmap of 124 bits for GSM 900. so the theoritical limit should have been 124 neighbors as each bit signifies a neighbor ARFCN.