Not likely what? A LIRR conductor works in Penn where calls come from, then goes back home to Massapequa where more calls come from. Why so many calls from Penn? Maybe your looking for someone who works there. Someone in a transit uniform on the surveillance videos from calls times isnt going to stand out. Many people have suggested transit cop. I could see an LIRR conductor striking up a conversation with Amber when the train is not very crowded, then finding her in Craigslist and when he calls Amber kinda knows him from her commute so her guard is down. I'd really like to a more thorough account of Amber's day to day schedule. Here's who we know she encountered daily: Drug Dealer, LIRR conductor, ?.
That's assuming that she went through Penn, from where she was coming from it would have been quicker to get to the hub in Jamaica Queens, or Brooklyn's Atlantic Terminal. Those are the other 2 major LIRR hubs in NYC, and both Jamaica and Atlantic Terminal have as much traffic as Penn. Similarly, you can score any kind of dope within a few blocks from all 3 hubs for about the same dollar amount per sack, cheap.
LIRR conductors work full shifts and have tightly regimented schedules. They don't get "calls," they have consistent train schedules that they keep M-F with more limited service Sat and Sunday. Typically, when starting or ending a shift, they get on or off the train respectively at a designated stop. They don't have leeway to get on and off whenever they feel like it. Additionally they work in groups. There's the main conductor, and then there's the groups of ticket punchers/door watchers. They're usually a two wo/man team, with a couple teams per train. It would be very difficult for a conductor to pick up a hooker on the train, and bounce with her without drawing serious and immediate speculation.
There are also LIRR regular commuters, which total a little south of 400,000 people per day. Usually the only people that conductors recognize and say anything more than "ticket" too when punching are older and have been on that same train, at that same time, every day, 5 days a week for 15 years.
If simply riding the LIRR is the connection, it'd most likely be a passenger, not a conductor IMO.