Generally, no mass transit system will be allowed to be towed while passengers are on board. The tug vehicles aren't made for the weight of the passengers' and when the vehicle fails you can't have confidence in the safety systems any longer are just two of several reasons, most of which result in higher liability. Since it would be impractical to train all of the monorail CMs to know "when there is this failure do this and when there is that failure do that" the safest bet is to have a single procedure that works for as many types of failures as possible. The monorail fails, you might not know that a wheel is "frozen", so you tow it and start a fire (something WDW is probably very sensitive to). The vehicles control system is down, you start to tow it and a passenger becomes distressed, the emergency communications system may not work. As far as power is concerned, they most likely lost one of their traction power substations that convert the commercial power to the 480v that the trains use, having a spare generator won't help that. I am not sure but based on the age I doubt they have adjacent station coverage where if they have substations A, B, and C, and B goes down A and C have sufficient power to cover the line section that is normally powered by B. It is common today but was not very common in the 70s and 80s.