AFAIK, no railroad generates its own power anymore. Indeed, the great
1930s Pennsylvania RR electrification used commercial power right from the start.Amtrak, SEPTA, and NJ Transit still have considerable routes that use the original 25Hz 11,000V. The New Haven to Boston line uses modern power as does some NJT routes.
The locomotives can switch power on the fly, but many of the commuter cars require shop work to make the conversion to a different power source.
AFAIK, today there is nothing wrong with continuing with 25Hz and a lot of expense and disruption to convert, so it probably will remain in service for a long time. AFAIK, the substations that convert the frequency are solid-state now.
A more pressing problem is the poor shape of the catenary (overhead wires to the trains). It is mostly 75 years old (or more) and time has caught up. Looking at it, especially at complex junctions, one can't help but marvel at the genuis of the engineers who designed it in the 1930s -- its durability is incredible.
[TELECOM Digest Editor's Note: I still recall how Chicago Transit Authority used to switch between 'third rail' and overhead (catenary) wires north of Howard Street on the Evanston line and the Skokie line. Train would pull out of the station (using third rail), get a short distance up the track, coast to a stop and while they were in the process of hoisting the catenary pole into place, one or more of the clerks would walk through the cars like the proverbial train bandits of old times, telling the passengers "five cents more to continue your ride, please". People would get in their purses to find a nickel to hand over, but thoughtful passengers who made the trip each day and knew what to expect had already paid their five cent surcharge at the station where they boarded the train and instead of a nickle for the clerk would produce a a scrap of paper instead which I think was entitled 'proof of payment' and hand that over to the clerks instead. PAT]