Yes. Usually... I mean I didn't test it specifically with 3G dongles but once I connected powered HUB, to which I attached second hub and plugged 3 gigabit ethernet dongles, 2 hard drives, usb RS232 serial adapter and some other random crap I had laying around. Everything worked and MikroTik properly detected all 3 gigabit interfaces and registered as eth6, eth7 and eth8. HDDs worked as well and serial console could also be configured to work like native serial. Considering that 3G modems are detected in similar manner to RS232 in RouterOS I'd say it's likely to work.
So my blind guess is - yes, it will most likely work. Especially 3G ones. Not sure about LTE.
MTCNA, MTCRE, MTCINE