We used to use Cradlepoint but there's limited space in these device boxes, hence the move to using Routerboards since we're tunneling back to HQ anyway. The LTE card is perfect for this application. We might try a MVNO that utilizes Verizon and see if they will be more flexible in their accomodations.
The LTE card is ABSOLUTELY NOT PERFECT FOR VZW IN THE US.
VZW uses 2,4,5,13,66
Band 2 (1900MHz): this is a band that Verizon is actively transitioning from 2G/3G for use for LTE. It is currently a supplementary carrier that brings more capacity to the network and is commonly deployed in 10x10 chunks.
Band 4 (1700/2100MHz): Verizon has solid amounts of these bands that it deploys in larger, 20x20MHz blocks in many markets.
Band 5 (850MHz): it is a band that Verizon is still using for 2G/3G services in some markets, while for others, it is using this band for LTE. Verizon holds a lot of this spectrum nationwide and usually deploys it in 10x10 blocks.
Band 13 (700MHz): this is the backbone of the Verizon Wireless 4G LTE network. Verizon has this rolled out to most markets across the nation, but since it is usually deployed in rather small 10x10 chunks, it could become congested fairly easily.
Band 66 (1700/2100MHz): this is a superset of band 4 (meaning that it has all the frequencies of band 4, plus a few additional blocks). It is usually deployed in small chunks and it not available everywhere.
Mikrotik wireless doesn't support 13 or 66.
13 Being the most used currently
I spent a lot of time looking into sierra online... but never used one.