Many taxi companies are actually dispatching outfits that license their branding. If you want to drive with their branding and receive their dispatch services and customers, you abide by their rules and pricing. You're an independent contractor, not an employee.
If that is the case Uber drivers will have to become licensed taxi drivers. Uber conveniently circumvented this on the argument that they are a sharing/collaborative economy startup, in turn saving themselves lots of money and gaining an unfair competitive edge. They can't use this argument as they have already cornered themselves in this regard.
In Santa Cruz Transportation, Inc. v. Unemployment
Insurance Appeals Board (1991) 235 CA 3d 1363;
1 Cal Rptr 2d 641, the Appeals Court held the drivers
who paid the taxicab company a fixed-fee to lease a
taxicab were common law employees of the company
Can they subcontract once they license the branding? If so, see point (6) of the thread starter comment. If not, I wonder if point (5) applies in that making licensing decisions is a "managerial" type thing to do. Seems hazy though, and it very well might be that it's no different than Uber, and those companies could be similarly ruled against. Lots of companies come up with schemes to treat employees as contractors, with varying degrees of success.
Uber's outcome on this case does not mean that there are no other companies that have not been discovered that are mis-categorizing employees, if anything, it's the opposite: Uber is mis-categorizing employees, so it's highly likely that other companies are too.
A taxi company that operates this way is at least close to the bar of having employees. You don't mention whether the drivers are allowed to subcontract work or not: if not, I'd be confident the drivers would be legally classified as employees.
This may simply not have been tested in court (or not in any newsworthy case). If you keep a small number of independent contractors happy enough, they won't split hairs over this issue.
How is that different than Uber?