Last Friday when I rode past the shops there were a couple of strings of new cars out there. One set was lit up, looking like it was going out on the road. And yes the numbers are both 5800 and 5100's.
Saw a 4-car set of the PA-5's testing on the line from the CSX yard this morning. It was an A-B-B-A set....looks like the "A" cars were 56xx-series and the "B" cars are the 51xx-series. Four other cars were sitting outside the shops at Harrison as I saw passing by on PATH a while later....