VM engineers can call on you without notice if they are fault finding in the area & suspect the issues is related to your connection, they can check at the dp cabinet for 'noise' on active feeds & identify the property (each feed in the dp cabinet has details of where it is connected). Common reasons for 'noise' on a feed are: faulty splitter, lose or open connection (internal feeds should be connected nice & tight or be capped when not in use).
VM tech department can connect to your router & see the devices connected by the name of the device or by an experienced tech who recognises the device such as a mobile phone but they ARE NOT permitted to dig any deeper into any connected devices as that would be an invasion of privacy, many users change the name of a device they don’t want to be identified via a network test.
Example: a Zgemmah2s when connected to your network will show as Zgemmah2s by default so changing its hostname to xbox will mean the tech doesn’t know your using a streaming device for TV.
If an Engineer at your door or an tech in an office suspects you are using a device for (illegal) streaming they have very little power to do anything other than ask you to disconnect the device so they can complete their tests.