Comment 4 for bug 1473246

I'm assuming those ttys are not to be treated as modem ttys; so long story short, you'll need to blacklist them for now in MM udev rules... I fixed this already in git master and the mm-1-4 branch for this specific MediaTek device, so will be available in the next releases:
http://cgit.freedesktop.org/ModemManager/ModemManager/commit/?id=0e7fc1dff9b3b8f72f6537f7f2b68e5c94a4c751

If you know of more non-modem devices to blacklist, please report bugs to the ModemManager bugzilla:
https://bugs.freedesktop.org/enter_bug.cgi?product=ModemManager

And yes, the blacklist is far from the best solution.