Just because it's called "City of London Corporation" does not mean it's the same as a public limited company with shareholders. It's basically a local authority with an unusual name and history(+). Of course it's very pro-establishment, but that's a function of its electorate.

PIPCU is new and a little unusual, although there's plenty of precedent for having special police units for complicated crime and they sit next to the Fraud bureau in City police units. It's a bit of an escalation - previously it was local Trading Standards who would handle piracy (e.g. people selling copied DVDs at the local market)

(+) How old? Over 1000 years, its origin is unclear.

http://en.wikipedia.org/wiki/Municipal_corporation

http://www.cityoflondon.gov.uk/about-the-city/who-we-are/Pag...

See the Reedy Creek Improvement District, for a US analog:

http://en.wikipedia.org/wiki/Reedy_Creek_Improvement_Distric...