It is not possible have simultaneous connectivity between two mobile operators with RUTX14. However, RUTX14 has an LTE Cat 12 modem, which, under certain conditions, is capable of achieving similar download speeds as two RUTX12 modems operating at once.
The RUTX14, as well as most of Teltonika routers have more than one interface through which they can reach WAN, in particular: moble, wired and wireless. Thus it is possible to distribute traffic between those interfaces. For more details, please view the video about load balancing in this link: https://www.youtube.com/watch?v=hgF1LZXSsvs.