ok, now for the dbus stuff referenced by location-proxy.
Relevant header files/bits:
http://www.cncmods.net/files/dbus/csd-ssc.h
http://www.cncmods.net/files/dbus/ssc.xml
http://www.cncmods.net/files/dbus/wappushd-dbus.h
http://www.cncmods.net/files/dbus/csd-sim.h
http://www.cncmods.net/files/dbus/sim.xml

Location-proxy listens for the com.nokia.phone.SSC.modem_state_changed_ind in order to detect the modem state changes (if the passed in state is "initialize" it sets some things up)

It calls om.nokia.wappush.register to register for WAP push notifications (see wappushd-dbus.h for the details of the WAP push stuff) and passes "x-oma-application:ulp.ua" as the URN, "com.nokia.Location.Proxy" as the service and "/com/nokia/location/proxy" as the path.

It calls Phone.Sim.get_imsi to get the imsi for setting the sim_imsi gconf key mentioned above.

It listens for the DBUS message com.nokia.WAPPushHandler.HandleWAPPush on the com.nokia.Location.Proxy service (again see wappushd-dbus.h for the details) and passes the message to the cellular modem (details of how WAP push supl messages work is likely documented somewhere given that its a standard of some sort, I dont know how they work)

It also listens for the dbus message com.nokia.ShortMessageHandler.HandleBinarySMSData. This is undocumented other than the dbus signature which is siiyyay. The only bit location-proxy cares about is the array at the end which is sent to the cellular modem (the format passed in is identical to the one passed in in the WAP push case and as mentioned is likely documented somewhere)