The California communities of Cupertino, Mountain View and East Palo Alto have begun to ponder new taxes based on employer headcounts — levies that could jolt Apple and Google — and if voters endorse the plans, a fresh wave of such measures may roll toward other corporate coffers. Alarmed by traffic and other issues brought on by massive expansion projects, the three Silicon Valley cities are pushing forward with separate plans to impose new taxes that could be used to make transit and other improvements. “If we are successful in putting something together and (getting it) approved, I believe other job-rich communities will try to put their own measures on the ballot,” Mountain View Mayor Lenny Siegel said.