@BadgerandVole reads like a point-to-point line-of-sight link maybe, so see if there's a matching one there (or take a walk in the direction it points if there's cabling into it).
also, if cabling, prob avoid standing in front of it just in case it's still powered up. the word "microwave" is used in the powerpoint that pic comes from, so directional 2.4GHz cookery is an option :D
@BadgerandVole microwave links are pretty linear, which limits range unless you go high. if you have line-of-sight it should be possible, power required increases with range. specs I can find seem to show that being linked *to* an optional microwave link, presume for backhaul to provider.
would have been a pretty nifty and not too costly way to get cell coverage over a few miles of water I guess.
@evilstevie wow! I don't think there's power to the building any more! I'm not sure what it might have pointed at - maybe it linked to a neighbouring island, or is it much shorter range than that?