Oakland/San Leandro BART tracks

[PaintPenRhetoric]

Last weekend I was on BART heading to the the Colusseum and I noticed that the presence of graffiti had changed a lot since I was growing up in the area years back. In San Leandro almost every wall facing the tracks was covered and recovered with graffiti, but once I crossed into Oakland it was almost completely blank. Lots of areas where it had been painted over but almost nothing to read on the way through.
Has Oakland really gotten that effective about painting over graffiti that fast? Or did I just time my trip totally wrong and hit it on a day when it had been painted? Or has the Oakland scene just moved away from Bart?