Definity G3si with Asterisk VM only

Does anyone know if it is possible to replace an Audix Voice Mail server with an Asterisk Voice Mail server? Our g3si switch currently has 6 analog lines that go into the audix vm server. I have seen guides talking about Asterisk pbx integration with definity g3si through the use of t1/e1 trunks. I do not have any spare t1/e1 trunk cards in the definity.

If analog lines are possible would I need FXO type ports on the Asterisk or FXS ports or a combination of both(I would need auto attendants that could forward a caller back to an extension on the definity pbx)? Also, would the MWI function still work with Asterisk? Thanks for any help.