I'm struggling to understand why they can't at least be prosecuted for theft as the items removed belonged to someone else. That's a pretty clear definition of theft is it not?
It is not
a clear legal
definition of theft.
A legal definition of theft requires "the intention to permanently deprive"
As such if CGM/NR have simply removed the camera and weather station and they are now waiting to be collected from desk in the ticket hall, then WH have not been permanently deprived of their goods and it is not theft. It might be some other offence but it is not theft of the equipment.
This is the reason joy riders are charged with "taking without the owners consent" rather than theft. In fact until that offence was introduced they had to try and prosecute then with theft of petrol.
So the question of whether it is theft or not comes down to whether WH has access to their kit and that is a fact that is not in the public domain at this point in time.
The moral of the story is the law is not obvious. I am not lawyer, but my siblings where, with one now being a part time judge among other things. As such you pick this weird legal stuff up.