I know a bunch of groups (fraternities and sororities) tried to fight the rezoning known as the university neighborhood overlay but were unsuccessful. I believe it was described as postponed.
here is the link.
http://media.www.dailytexanonline.co...-2992623.shtml
Talking with friends who are their respective alumni boards they are trying to find out ways around the system. But really when it comes down to it, the best way to not pay as much on the property taxes is to protest them.
I was an ATO at UT and know we protested our property taxes using the same group that KA SIGEP and Acacia used. I think when it was all said and done they saved all those organizations on their property taxes.
I'm not sure if you were familiar with protesting but it doesn't completely eliminate property taxes. It just saved us some money to use on more important things (such as repairs to the house, alumni events and so on).
In regards to the fraternity houses moving, I do not think there is any way. There is no where for them to go. Until something changes with this overlay what fraternities are left need every break they can get. West Campus is probably the only area where the houses can be somewhat tolerated. However, every few years the city makes a push to attack them.
And if kids keep dying or houses making major news stories around the country then property valuations will be the least of our worries.