There's no need to "reverse engineer" anything. The source code is freely available. You can either extract it yourself using methods already posted in this forum or look online to handfuls of sites that have it available to view. I even pointed out the specific Lua file that handles their battlegrounds UI.
Extraction Method:
http://www.wowpedia.org/Viewing_Bliz...interface_code
View/Download UI Files:
https://us.battle.net/support/en/art...face-addon-kit (Multiple languages available, downloads UI in a Zip file.)
https://github.com/tekkub/wow-ui-source
http://wow.go-hero.net/framexml/builds