Perhaps LTE is better than older 3G/HSPA, but cell towers don't always give the right time - actually, time's usually okay, but date might be many days off (so on Thursday, your data has Tuesday's date). Or you might get a date/time like Jan-1-2003, etc. Apparently, cell towers giving time is an "optional feature", so not all do it. Also be careful because you'll get local-time, so make sure you parse & handle time-zone correctly.
NTP is probably overkill for a small cellular 'sensor'.
If you are using HTTP/HTTPS, then the safest solution is to use the required (not optional) UTC DATE field in the server response, which will be like "Date: Mon, 21 Nov 2016 21:11:56 GMT". I do this, plus have a 'tolerance' like 10 seconds, so don't change my RTC unless the server UTC is more than 10 seconds off.
To 'boot-strap' my RTC, I embed the FW build UTC in the firmware, and upon boot, make sure the RTC is never 'older' than the FW build time.