E&M is a trunk interface, either 2 or 4 wire, generally for switch-to-switch connections. E&M can support DID whereas FXO cannot. You're more likely to find E&M interfaces on a PBX than a key system unless your key system had analog DID lines.
An E&M i/f connects to another E&M - an FXO connects to an FXS.
The most common interface will probably be an FXO. The issue is really cost. You may get more functionality from an E&M, but on a PBX you need the E&M trunk line card(s) rather than just a couple of station ports. The telcos, at least in my area, would rather not provision analog E&M. They're happy to sell you POTS (FXO on your side) or some flavor of T1.
These are the paths to get to each CCX logs through CLI. They may be helpful if you are having issues accessing RTMT or downloading logs through it.
If you want to download them you have to prefix "file get " and you can add one of the options (re...