Yeah, LBJ and LASA got along so well that they have now physically separated the campuses. AISD built a new home for Eastside Memorial at the original LC Anderson campus, moved LASA to the old Johnson campus, and kept LBJ at LBJ. The district is shrinking but it's politically impossible to combine or close schools, so many schools are seeing lower enrollments.
In Austin ISD, you can transfer anywhere there is space available, and there is space available at all of the high schools except Bowie and Akins. You can also transfer into the district. I don't think AISD intended to create an unofficial athletics magnet at LBJ but I think they have.
For this realignment cycle, AISD opted-up four schools to 5A-D2. Do they want to get killed? No, I think they want to create their own 5A district within the school district. So LBJ will be crushing Eastside, LASA, Travis and Northeast rather than traveling to play 4A schools elsewhere.