Looks like they're spot replacing the MV/MH GE M-400R3s on the I-190 Grand Island bridge with these LED fixtures. If I remember correctly the M-400R3s and the davit arm were retrofitted on to the poles which used to hold truss arms.
Yeah, all of these on the south bridge got zapped with only a couple of GEs left. The north bridge has around 3/4 of the old GE M-400R2s and M-400R/A3s left though.
I saw around one LED too in the summer of 2011 so I guess they might be spot replacing the GEs as the lamps fail or they haven't gotten to the rest yet.
Actually, the history behind these is this. These davit retrofits replaced truss arms with 400 watt MVs. The South Grand Island Bridge had GE Form 400s and the North Grand Island Bridge Westinghouse OV20s. The davits had Holophane luminaires with 250 watt HPS before being replaced with the MH luminaires.
I saw around one LED too in the summer of 2011 so I guess they might be spot replacing the GEs as the lamps fail or they haven't gotten to the rest yet.