Parimutuel betting works the same way regardless of what you're betting on. It could be thoroughbreds, harness racing, or jai alai. Technically, you can offer parimutuel wagering on anything, even football or car races.
Sure, but the various features which make a harness race predictable are unlikely to make other kinds of horse race predictable. Sorta like Steve Skienna's jai alai system is unlikely to work on horse races.