last time i read the nya/lirr lease, nya was renting power from lirr at truly high rates. i was of the opinion that they would have needed all 9 locos to pull a 30 car stone train to brt. i don't think that move materialized. if it had, nya would have had to use the ya run-around for a pulling move to brt then shove back to ya. with smaller moves nya can use hind end power.
i don't believe nya has excess power to lease to brt.
now as for gp38's, they are fuel hungry, road gearing and vision -restricted for close-in switching. i recommended a sw1500 and a different track configuration. i can opine as to why the gp's are leaving. ken patrick