Yes, I think it's worrying, because its interests will not align with the interests of the general public or even those who pay for the 'private police'.
It is a basic principle of British policing, established with the foundation of the Metropolitan Police in 1829, that the test of police efficiency is the absence of crime and disorder, not the visible evidence of police action in dealing with them. Yet for such a private police force their profit comes from the "visible evidence". It is in their financial interests to convict the most people for the worst offences for the least money, and not in their interests to reduce crime levels, to take on cases where an acquittal is plausible, or to give a damn whether the people convicted are actually guilty or not. If the private police feel they can get away with trumping up charges, planting evidence, and framing people, they will.
We've seen in recent-weeks high-profile examples of court cases collapsing or being overturned because the regular police hushed up evidence that would count against a prosecution. I believe this to be the tip of a very big iceberg, that police up and down the country are doing this routinely, that innocent people are sitting in prison cells because the evidence that would have acquitted them has been unlawfully hidden or destroyed. And that's the taxpayer-funded police; it will only be an even greater issue for private business.