I just installed the latest CM unofficial build (cm-11-20140227-UNOFFICIAL-lt01lte) on my new SM-T315 and it's working well. LTE works (I'm on Fido in Canada). Both cameras are working. The only weirdness is the GPS toggle from the quick settings doesn't work, but the GPS itself appears to be working fine via Google Maps. I also installed the standard GApps via http://forum.xda-developers.com/show....php?t=2012857
I flashed via TWRP 22.214.171.124 rather than the recommended PhilZ Touch recovery, but it seems to have worked just fine.
I don't have enough posts to comment in the development thread, but I just wanted to say thank you. Also considering I see so few posts from T315 (Tab 3 8.0 LTE) users, I think it's nice to see when people confirm something is working, so I thought I'd do the same.