Good luck ant getting a track in a city. I bet if you contacted City Urban Parks and Planning youd find them open to the idea in an existing city park like Braddock was in. Also many cities have large abandoned old factorys etc that an indoor track could go into. Might take a grant to get it started.
Red Pony indoor was in a barn in Lakewood. The Amroy was in an old govt building in Jersey City. You just have to think outside the box also. For instance and old supermarket in the city would be big enough to house an indoor track, freestyle area and Pro Shop. Try getting a grant and a partnership with a bike shop. The shop puts in a pro shop to pay for the lease. The city gets taxes from the bike shop sales and payroll. The city turns an empty building into something positive for the community and for its youth. Could even make it so so low income reisdents get to race or ride the park for free and make sure that a loaner bike and helmet program is set up from day one, so the newspaper and city knows everyone can get into BMX. No rider left behind.