I successfully sent a telegram from SP12, via the coach porter and the operator at Dunsmuir. I once tried the procedure for sending a telegram to a train passenger and it did not reach him.Back then, there weren’t cell phones. You might have been able to send a telegram to a downline station…
In Edmonton there was a CN business car stub track. Business car parking tracks were often provided with phone and/or telegraph connections, but I'm sure there were times between stations when a superintendent was glad that Montreal could not reach him.