We use the term Alternator in the Supply Industry, to denote any equipment that supplies AC energy, with the use of a Prime Mover.
Also, no, the equipment is not mounted on the pole, ever seen the size of a Transit Container?, (the sort that they use on Ships).
Essential supply is run by the Lines Company, where the supply is NOT allowed to be turned off.
I have installed a lot of Essential supplies to houses, here where the owner has just come home from Hospital and is on a personal Dialysis machine.
A small break in supply is allowed, but with the installation becoming a Electro-Medical installation, you have to install 10mA RCD's (as opposed to the 30mA ones)
Contactors are used to transfer the voltage over and when the Mains drops out, it triggers the Generator into life.
We supply these Generators free of charge to Dialysis Patients, as well as the Fuel,installation and maintenance, they have enough to worry about, why compound things?.