Practice "sharing" between teams?

This may well seem like a crazy idea, but it occurred to me yesterday, so I'm investigating to see where it might lead. In Evanston, IL (pop: 75,000) we have four masters teams: YMCA (MYST), YWCA (Flying Fish), Evanston High School (Wild Catfish), and Northwestern (NASA). Practice times vary between the different clubs. All seem to have evening and Saturday workouts, however, different teams also have other practice times. For example, NASA has three noon practices a week. The Wild Catfish have Sunday morning practices. MYST and the Flying Fish each have at least two early morning workouts on weekdays. Currently all four teams are completely independent. A few people swim with two clubs, but they've joined both. Given the wide range of available practice times and the concentrated geography, it seems like it would be very handy to be able to choose among the various practices, at least on an occasional basis. Can't make it Saturday because of your kid's soccer game? Do a Sunday morning practice. Out of town on Wednesday? Hit the pool Thursday morning. Has this concept already been tried elsewhere? If so, what obstacles needed to be overcome to make it work? Fees? Balance? Overcrowding? Did/does it work? If not, why not? Thanks, Skip Montanaro