The geometry and construction of the 186 and 196cm lengths of the Bibby Pro were very similar to each other, but very different from the other (174, 184, 190) lengths. So for 2013, the 186 and 196 are now the Governor, and the other lengths (as I understand it) remain the Bibby Pro.
The most significant differences between the lengths that remain the Bibby Pro and those that are being rebranded as the Governor are the sidecut, rocker profile, and flex.
The lengths that are becoming the Governor have a pintail geometry at 150/116/123, while the lengths that remain Bibby Pro are more symmetrical at 143/118/134 -- that's three times the taper from tip to tail in the Governor as in the BP.
The BP lengths have 65mm of tip and tail rocker, but the Governor lengths have a 55mm tip rocker and only 10mm of tail. That translates to 164cm of effective edge in the 186 Governor, compared to only 156cm of effective edge in the 190 BP. (The 196, which I own, has a whopping 174cm of effective edge, which I believe is the most on any commercially available rockered ski, and translates to fantastic performance on firm surfaces for a wide, rockered ski.)
The Governor lengths are also significantly stiffer, as I understand it.