Here is the link for the IBA Lighthouse Tour, http://www.ironbutt.com/lighthouse/ . It does not seemed to be linked off any of their other pages. I found it by searching the IBA forums. Looks like they just initiated this in 2010. It might still be getting it's legs but looks like it is ok to start once you get your IBA flag.
I have an .xls and a S&T file of the VA, DE, MD, NJ, PA, and NC locations. Note that the rules say only lighthouses from the US LightHouse Society, http://www.uslhs.org/, are accetable. There are seveal other lighthouses listed with LightHouse Friends, http://www.lighthousefriends.com/, that apparently are not acceptable.
Anyone in NOVA interested in doing some of these together let me know.
The IBA forum thread on this does indicate now from the tour leader that ALL lighthouses are acceptable if they are legitimate lighthouse, i.e. e.g.not somethat that looks like a lighthouse at the Lighthouse Mall.