There should be no reson that I can see to change the Monitored house code from 0x06 (I'm assuming your talking about the hard-coded monitored house code in DevicePoll::SendClock()). The interface will receive on all house codes regardless of what the monitored house code is set to. The only time that function is called anyways is pretty much if the power goes out and comes back on, or when you first plug it in.
After a lot of reading, what the monitored house code appears to do is store the state of all devices for the specified house code. (So the CM11A has a 2-byte buffer, with the 16 bits representing on/off for all of the device code for the monitored house code). That way, when a power outtage occurs, the interface will send a timer request to the PC (0xA5) to resync the internal time clock, and set the house code to monitor states on.
After this point, if we send the CM11A a status request (0x8B), we can obtain the stored status of all the devices on the monitored house code.
(This is what I understand of it anyways, and I think i have a pretty good handle on it)
I don't believe LMCE uses this information anyways (though I haven't really looked yet), and even if it did, it would not be all that useful in the context of LMCE.
and on another note, I'm going to do some tests with motion sensors tomorrow