For Shared Lines when clustering over the WAN, there may be advantages too. For example, if you have extension 1000 in Site A and Site B and each have a CCM subscriber. If the WAN link is down, the extension 1000 can be still be reachable on both sites, but to different phones.
Who knows, some people have such queer requirements.
And why it is not recommended is in the SRND under "Considerations for Shared Line appearances" or page 119 of the SRND for CCM4.x.
Cisco actually recommends not to deploy shared lines due to additional WAN Bandwidth taken.
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...