Actually, Klingons often transport when cloaked - Kirk used that ability extensively in ST4, and it played a role in "Unification" as well.
It's Romulans who insist on stopping everything else when cloaking, and conversely in dropping cloak when doing anything at all. This also affects the Defiant
, with its cheap Romulan cloak.
The proper question here is, who the hell would want to board a mining rig? And why should the rig try to prevent that? Merchant ships today don't try to stop boarding parties capable of getting aboard a speeding transport, because if they are capable of that, they are also capable of sinking said ship; it does no good to resist, and a world of good to surrender.
Actually it's a very OLD concept that nobody could ever get to work properly. The first experiments with transwarp beaming took place in the 22nd century not long after the development of Starfleet's earliest transporter systems; Trip even mentions to Archer that the modifications to the transporter were mainly just superficial and despite the increased capability of their transporter system, didn't seem necessary for transwarp beaming anyway.
Quite so - and quite consistent with the TNG "Bloodlines" portrayal of subspace-enhanced transporting, too.
Getting it to work is "new", and different from how regular transporters work, though. Again, the "Bloodlines" system is sufficiently different that it sidesteps shields which are the perfect remedy to conventional beaming.