I've said this before - but access to the power plant property will, in all probability, never be granted. It's considered critical infrastructure - and in addition to corporate / security barriers, there's likely state/federal regulations that would prohibit anything that puts the reliability of the 'grid' at risk from occurring on their property. Especially for a request by some hobbyists.
That and even if access was granted - you gotta rebuild the track and connection to the spur off the CSX Albany Secondary. That and the switch on the CSX line into the plant appears to be gone. So your only realistic option is the bridge to the north over Normanskill Creek... which from what I've seen looking at pictures of it - I wouldn't want to walk over it - let alone try and pull 200,000 lb locomotives over it - half of the plate-girder span is gone and what's left doesn't appear to have much weight bearing capability. The trackage in and around the plant likely hasn't seen any moves since the 1980's (the plant was converted from coal to oil in 1970) - so who knows if anything could be moved over it safely in the first place? However, if one of those pieces of equipment causes the bridge to fail and a locomotive takes a bath - now you're dealing with the DEC, removal and clean-up costs, etc.
It's a shame. I saw some pictures of the electrics from the 1980's when they were restored (at least cosmetically) and looking great. The time to move them out of there was before they could be landlocked. 30 years later - and they're rusted junk. The only way those things are leaving is in pieces in a dumpster to a scrap metal dealer... but realistically, they'll continue to sit there for decades until the property is developed and the stuff scrapped. The topography between the nearest accessible road and the siding is too steep and would prohibit moving those things out on low-boys unless you brought in a lot of fill and gravel - and then there's the assumption that the local roads could support oversize/overweight loads, and further assuming the utility will allow this type construction to happen on their property under 115 kv power lines. There's also the barrier of the CSX line too. And don't even think for a second that CSX will allow this stuff to move an inch on their rails.
Besides, doing some research, the equipment is no longer on utility owned property. It was all pushed back beyond the utility's property line onto a piece of land owned by Beacon Harbor, LLC who has plans to develop the property into a waste-to-energy plant. You think they're gonna wait around for a museum to raise funds to get their stuff out of there or going to figure out who owns it? Again, abandoned property on private property. If the stuff is in the way, it's gone.
Rough estimate, assuming you can get the necessary clearances, permits, etc... you're looking at $750,000 - $1,000,000 in costs to move that stuff out of there intact. On top of that - you have to deal with property access issues, insurance costs, etc. Other than some eccentric railfan/history buff type coming along with very deep pockets - you're not gonna get the funding needed for this.
Call me negative, but this reality.