What happened to IRT Power Plant on 59th Street

What has become of the IRT power plant on 59th street?
I would assume the old substations have been modernized and are still in service.

The entire structure still stands, now used by ConEd.

Most (but not all) of the old substations are still in use, upgraded from rotary converters to transformers and solid-state rectifiers. Progress is inevitable, but it used to be fun for a kid to peek into the substations when the rotaries were running.

Many of them still read "IRT CO.", such as the one along the #7 on Roosevelt Avenue across from Shea Stadium.

If you're interested in these stations and haven't seen it already, New York's Forgotten Substations: The Power Behind the Subway is a good read and has some nice photography. Available on Amazon.