Did SF police expect a Thurs BART demo?

In SF on Thursday, police expected a protest
at or in a BART station.
I noticed SF cops massing in street near SF Main library, around 6 to 8PM Thurs..
Meanwhile, BART disabled cell phone service in some SF stations;
trying to disrupt or prevent a protest.
...
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2011/08/12/BAEU1KMS8U.DTL
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Did SFPD cops waste thousands of dollars,
waiting for protest that didn't happen?
.......
Ordinary passengers suffered
when BART cut off their cell-phone access.
Was the cut-off lawful???
...
PS-- Don't let BART or SFPD know about
non-violent nude-in
planned for Sunday, 3PM,
at BART Civic Center station.
[during Sunday Streets event]
......