This is from their light sizing guide... http://4fishtank.com/lighting%20choose%20chart.xls
Tank - OV 110 U-shape room divider
Dimensions - 48x18x30 (48x20x180 is the 120)
Fitting length - 36" ~ 45"
Freshwater fish only -fluorescent 60 ~ 150w
Freshwater fish and plansts - fluorescent 120 ~ 260w
Freshwater densely planted - fluorescent 220 ~ 330w
Salt water fish only - fluorescent 60 ~ 150w
salt water fish and live rock - fluorescent 120 ~ 260w
corals moderate lighting - fluorescent 220 ~ 480w
corals intense lighting - metal halide 430 ~ 800w
What this appears to mean, is that the U shape will accept a 36 inch fixture on the edges and a 45 inch fixture in the middle. It is not stated how wide that middle fixture can be, as on side will be the curve.
Best bet is to go with 36 inch fixtures and stagger them to cover the area.
Looks like a very nice tank, stand and canopy.