A lot of security guards wear official-looking uniforms (including cammies). Unless you can read Chinese, you can't really tell they're cops or soldiers. I've noticed that some bank security guards carry guns, which sticks out, given how few *cops* carry them.
Reading that, I do recall an armored car parked at a bank, with guards holding riot shotguns. I do not read Chinese, so I do not know exactly who they were, but the vibe they gave off was "high grade private security" not "cop."
I also recall being a bit surprised that they needed three guys holding shot riot shotguns to guard an armored car.