The E1 calls are ofcourse compressed at g711alaw and 64k and that is a standard on which we do not have an option. An E1 to E1 call will only be able to use G711ulaw, same true for any pots to pots call. The only place we do have an option, hence the whole point for VoIP, is when you send the call out over IP or FR or ATM, and can compress it at much lower bit-rates so as to save the bandwidth. I do hope that I understood your question correctly, if not please let me know.
Hope this helps.