If CRS can send an email, you can make this work with email-SMS gateways out there in wonderland. A similar question was asked recently for SMS from CVP. Search - you may find it relevant.
Whoops - that's for outbound. Now I read it again and you are interested in SMS inbound. That's a bit harder - you need an SMS-email gateway in house that sends emails to a well known address, and have CRS monitor that POP3/IMAP mailbox and have email agents. The basic one should work - or you need EIM.
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...