Good knowledge, but there is a little RJ11 cable which probably goes out to a PSTN phone line for backhaul. I would agree with the other comments that this kit looks pretty old and I would expect is no longer providing any service. The cost to recover is probably too high so it will likely never get collected.It must be using the existing radio network as no other network connections apparent, theoretically that black network cable could be going to a router but unlikely.
So it's either a picocell using the local mast as backhaul or just a plain booster.
How old is it? It's entirely possible it's only 2G/3G capable so may not be effective now 3G is being dropped to give space to 4G/5G data.
If you fancy an experiment if you have a phone you can set to 2G only I wonder if that would show a strong local signal?
If I was to place a bet now if it's been there for a while probably a picocell that used the 3G from a local mast as backhaul that may very well have dropped off the network during the withdrawal of 3G and no one's noticed. Usually if a cell looses its backhaul the access radio side will shut down.
I'd be ringing Vodafone and quoting some of those serial numbers to them - I'd start with the business side not retail.