Wow, I didn't know it gave site access also!
When you push a site into battle, the heroes in battle gain access to any soul held in a site of the same brigade. Since Dragon Raid, Ends of the Earth, and New Jerusalem have ALL colors, it essentially opens up any site.
Note, however, that it is not a "site access ability" that would be negated by King's Pomp. Instead, it is a game rule allowing access (just like same-brigade heroes gain access to sites by game rule).
