As far as I know, the only legal solution is that one car gets to enter the intersection and then turn left after the signal has gone red. Of course, that's often a terrible answer - clearing one car per light cycle is a route to spectacular gridlock. (And with Boston drivers consistently running newly-red lights or blocking intersections, you sometimes don't even clear one car per cycle.)

Wikipedia does hint at a legal kludge, though - "I judged oncoming traffic to be moving so slowly that I could safely turn". The idea I guess being that it's not a change to driving rules, it's just slow acceleration and a legal turn.

I can't imagine that would hold up real well legally, especially if people are flashing headlights and making an invitation. On the other hand, I've never heard of this leading to a ticket in Boston - it just can't compete with the other violations that happen constantly!