This is a rather irresponsible article. The bill as passed by the CA legislature [1] addresses this possibility. In section 2, Section 22761(e) of the code limits the scope of law enforcement use in accordance with section 7908 of the Public Utilities Code [2], which prohibits interruption of communication by law enforcement in anything other than a hostage or barricade situation, ie an ongoing standoff between polic…
Your comment, on the other hand, does not accurately describe the relevant law.
PUC 7908 states that "If a governmental entity reasonably determines that an extreme emergency situation exists that involves immediate danger of death or great bodily injury and there is insufficient time, with due diligence, to first obtain a court order, then the governmental entity may interrupt communications service without first obtaining a court order as required by this section."
Your statement that PUC 7908 prohibits interruption only in hostage or barricade situations is incorrect; those are referred to in PUC 7907, which discusses cutting phone lines. PUC 7908 involves cutting cell service, and is more broad - it uses the language quoted above.
I could easily see this applied to a protest; police say a protest will lead to looting (e.g. Ferguson), perhaps they even see plans for flash mob robbery on social media. On the basis of this, they brick every phone in a protest zone, undercutting protest organization and limiting demonstraters ability to film police abuse on smartphones.
I do not know what the legislators intended; maybe they don't know about the issue, maybe they don't care, maybe they think this is an adaquete solution and are wrong. I don't try to define their intent here, I'm simply trying to point out a very real problem with this law.