(note i havent used asterrisk, i magage switchvox pbxes, based on asterisk)
g729 is normaly the issue as digum(i think) need you have a licence per channel (concurrent call)
however you should be able to have the phone itself set to g729 you can use bypass mode and not pay for the licence.
I could be wrong however i think asterisk is the same.
G729 support in Asterisk is not related to whether someone needs their Asterisk to use G711. I haven't looked at how Asterisk supports G711 as distributed bundled with LMCE, but it's usually a matter of just installing the codec in Asterisk
. Asterisk's installation UI is usually the commandline, so LMCE could do a lot better job administering it.