A Change.org petition was helpful in securing changes in zoning that are more supportive of accessory dwelling units.

On Nov. 19, 2015, the Austin City Council voted 7-4 to loosen the rules restricting the construction of backyard cottages. Led by Gregorio Casar and Steve Adler, the new rules let homeowners build granny flats that:

1) Only one parking space required, and zero required within 1/4 of a mile of an Imagine Austin corridor that has a CapMetro line.
2) Can build an ADU on 5750 sq ft of land, which is the standard lot. They used to require at least 7,000 square feet.
3) Reduced setbacks so its easier to fit the dwelling unit on a smaller lot
4) Can build an ADU to .15 FAR (up to 1100 sq ft) instead of just 850 sq ft
5) Only SF-3 is eligible, not SF-2 – which are zoning codes that can roughly approximate to urban vs suburban.
6) Enables all applicable properties across the city to build a granny flat. Establishment neighborhoods will no longer be able to “opt-out” of their fair housing obligations and push people to live in other neighborhoods.

Source: https://www.change.org/p/austin-city-council-allow-granny-flats-and-other-small-houses-everywhere/u/14276434