Sounds very dodgy , if someone calls 999 and asks for help ( or even if it’s a silent call or they ask for something odd , like ordering a pizza hoping the operator realises the call is an emergency but the caller doesn’t want to alert another person to the fact that they have called 999 ) then the call is held and traced and the police ( having got the address from the Telco ) attend the property, the call is held until the police ask ‘BT’ to remove the ‘hold’ from the the line , as they have established the ‘line’ that made the call or decided it doesn’t need holding .
If this supposed call was to a control room what was the control room , presumably it wasn’t the ‘BT’ 999 operator , who ‘holds’ the call , stopping any other calls being made from that line , and then puts a call through to the appropriate emergency service , police , ambulance, fire , and connected them to the line that made the 999 call and stays on the line .
If this call was directly to a ‘police’ control room (an ordinary phone number not 999 ) , all the police could do is try ‘1471’ which reads out the last number the line received a call from , provided the caller didn’t use ‘number withheld ‘ , and even with a phone number they wouldn’t have the wherewithal to do a reverse number search to get an address from it , and with literally dozens of service providers , calling ‘BT’ to ask ‘is this one of your numbers and what address is it linked to ‘ wouldn’t work if the number wasn’t even a BT customer and BT only have around 25% of the market , so a 75% chance BT don’t even provide the ‘line’
