hi nik,
since lcr uses alaw (optionally ulaw) internally, it transcodes the audio between alaw and gsm full rate.
alternatively you can bridge rtp directly between freeswitch and openbsc, if you use the "bridge <interface>" feature at interface.conf. additionally you need to add a line "rtp-bridge" to your interface definition. this rtp-bridge feature only works with the bridge feature, since lcr will not be able to handle audio streams then. since it is still developed, you need to use the "jolly/rtpmux" branch of openbsc. then it will only offer the codec to freeswitch which the phone supports. on the other direction, lcr selects the commonly supported codec. if more codecs are supported, the upper most (prefered) is used.
anyway it should work in both cases. (with and without rtp-bridge feature)
regards,
andreas