Ah, so it'll be unlikely to pollinate; and, if it does, the seeds would likely be sterile.
Assume that I can get them to pollinate. How many seeds would I get? What's the germination time?
With genetic modification, you usually put a particular gene on a cassette (a DNA ring in certain bacteria) and use that to inject the gene into some plant material, which you clone; there's about a 1 in 100,000 chance of successful injection, and it may take 100 or so trials to get something useful. Then you have to breed the modified plant and select for improvements in the injected trait.
With hybridization, it's similar: plants that produce hundreds or thousands of seeds or spores may have very few germinate successfully; from these few, you may get boring results (i.e. a gene combination strikingly similar to one or the other parent, rather than a good hybrid). It's a matter of controlled pollination, followed by sewing everything and seeing if you get anything good. If I get 1000 seeds out and 2 sprout, I'm on the right track.
Obviously, foxes can't breed with rabbits; that's always a possible outcome. On the other hand, asses can breed with horses, and have produced fertile mules.