The last time I saw a Guardian Angel "soldier" on the Subway was back when I was in high school. Since then I guess crime overall, especially in the NYC subway has gone down quite a bit. But with the recent surge in subway slashings I guess the Guardian Angels saw it as a sign that they should come back in full force to protect the NYC Subway.
The Guardian Angels aren't an official police force. They are just a bunch of do-gooders in the NYC subway that sometimes get into controversial situations because of their eagerness to take crime into their own hands.
I'll be keeping my eye out for these guys next time I ride.