heres the reason (simply put) that the VM network engineer was in your garden:
VM's system (nothing to do with wireleess transmissions) can leak RF into other systems using the same transmission freqs,which can degrade their service,a particular worry is leakage (egress) into (ingress) a close-by emergency services system.
they are legally bound and monitored by OFCOM to keep the leakage under certain criteria.each principal technician from the service side of VM has a monitor (manufactured by TRILITHIC for these purposes) in his van which picks up 'hotspots' of leakage from VM's network.
these guys then park up at the office or stores where it downloads its info.this info is then transferred onto a map with its measurements,the high leakage points then have a fault ticket raised which goes to a network engineer to investigate.
they have small handheld RF 'sniffers' which generally locate the leakage,but for awkward jobs theres a bigger aerial type device they use.
typically its unterminated connections on the network that are egressing but it can be an open-ended cable in a customers house or an output on a splitter or an open box on the front of a house with an unterminated cable in.
these cases of course are reliant on the 'drop' cable still being connected to the network.
hope this helps
