If a man is hit and killed by the T, does it make the news?

Suicides in public places are covered if the circumstances were unusual or if a lot of people were directly affected. It's not just the "in public" aspect that gets media attention.

When I've taken courses for clinicians on responding to community trauma, they'll go over how and why media coverage occurs in response to various events. The clinical recommendation is that suicides aren't publicized, unless what happened was so public and sensational that media coverage is actually going to help the community deal with the tragedy (for instance, by dispelling rumors and hysteria). The recommendation is generally that you do a community debriefing with the people who are affected. This is usually someone's school or workplace. Accurate information about the event is provided, along with information about the normal grief process, as well as what to look for if someone is reacting beyond normal grief, and where you would get them help. The media is usually respectful in not reporting in these instances, because the event isn't super newsworthy unless it was done in a really public and/or sensational manner (suicide by cop, etc.), and they don't want to get involved in a huge mess by reporting on something that isn't huge news and that's likely to upset people, possibly lead to copycats, etc.

A T employee who I know quite well was telling me that suicides are really frequent, and that most of the signal problems and whatnot are suicides or attempts. Most are not reported anywhere. This person also said that most people don't do it in a crowded station during rush hour, but are more likely to sneak off into the tunnel or jump, say, in Dorchester between stations (where the tracks aren't underground).

(FWIW, the general recommendation from clinicians is also not to create a public/lasting memorial when someone commits suicide, especially if it's a young person, because then you end up having kids several years later who only know that such-and-so has stuff named after him/her, but wasn't around to hear everyone being angry and frustrated with what happened, so it tends to make suicide seem appealing. It's usually more appropriate to do something like hold a memorial event, make a communal work of art or something to present to the surviving family, but not create anything public.)