same E1 for more than 1 BTS(sharing)

What is E1 line?
In telecommunications, where a single physical wire can be used to carry many simultaneous voice conversations, worldwide standards have been created and deployed. E-carrier system, which is revised and improved version of the earlier American T-carrier technology.
Now it is widely used in almost all countries outside USA, Canada and Japan. The line data rate for E1 is 2.048 Mbit/s (full duplex) which is split into 32 time slots, each being allocated 8 bits in turn. It is a ideal for voice traffic because voice is sampled at the same 8khz rate so E1 line can carry 32 simultaneous voice conversions.