This used to be done quite often but, as you said, that was 40 years ago. Under ideal conditions the POCO is supposed to come out after being notified that the service upgrade was complete. At that point they cut off your bugs (or whatever you use) and replace them with the crimps that they use. EC's used RX connectors KNOWING that the POCO would be out in a week or two to make the change. We are no longer confident that the POCO will come out in a short amount of time anymore so, RX connectors should not be used.The only time I ever heard of Electrians using Romex connecters for terminating a service was after a hurricane when they said the utilities were right behind them making them them up the next day and that was about 40 years ago.