One other place that hasn't been mentioned is the paper industry. At least here in Maine, there is still one mill (I know for sure uses, and others I've heard have) that have hydro generators and many 2 phase motors powering machines. Some power is derived from a Scott T though. There is also 11kv 3p and 2300 in house. I believe the 2p distribution is 2300 from the hydro dam, possibly 11kv, it's been a few years since I was there and know both voltages where common. 2300 was common in 2 and 3p. Most of the motors are 440 though, and a few @ 2300. I've worked in the substations and chased out circuits through miles of tray there. Knife switches and open bus is the norm in the oldest indoor subs. The mill Has been electried for 130 years and has all kinds of artifacts that no one would touch today, while hot.
Or steel mills, as in around the Pittsburgh area, the first poly-phase generator plant installed was by Tesla and Westinghouse at Niagara Falls, they used 25hz (one hz over the frame rate of motion picture to prevent the Edison lamps from strobing) and 110/220 volts or 220/440 as the customer end standard voltages, the 110 came from the fact that Edison lamps used 100 volts DC so 110 volts @ 25hz would give the lamp about the same brightness, and it would also last about the same amount of time.
Many of the old 2? 25hz motors were very large for their HP size, a 10hp would be as large as a 100hp motor today.
At the steel mill I work at today we still have allot of old switch gear no longer in use but still marked 2? 25hz, 110/220 or 220/440 volts, this is why we still hear old timers still refer to these voltages, once 3-phase made it to main stream the voltage standard was bumped up a bit.
The last 2? motor I had to work on was an old 500hp draw bridge motor, we had to install a 3? motor gen-set to produce 25hz as 25hz wasn't available and drives was non-existent back then.