I think these phones in a rack boxes are likely more oriented towards automation of apps, and can use ethernet via tethering rather than mobile networks. Could probably leave the top of the box off if you need mobile networks to work a bit.

The sim boxes used for bulk messaging / calling from the photos posted yesterday had antennas poking out everywhere. If you wanted these phones to work inside metal cases, you'd probably want an antenna per phone sticking out as well (or a shared antenna, if you've got rf skills)