I've had a quarter-acre sized plot of Round-Up resistant fescue going for three years. It is a variety of Festuca ovina, or sheep's fescue, sold in France under the name "Aurora Gold".
We have what we call "natural zones", which are out of the way areas that get minimal maintenance, no fertilizer or irrigation, mowed once a year in the autumn. They are a mix of dozens of species of grasses. Because we enjoy a rich topsoil with plentiful rainfall, these areas become very thick and heavy, and anyone who does hit a ball in there can write it off.
My idea was that if I could establish a fine-leaved fescue that tolerated Round-Up, I might keep out the other junk, like tall fescues, bentsgrasses, bluegrasses, and various pasture grasses, then it would be possible to maintain the stand in such a way that errant balls could be found and played out.
Well, as it turns out, yes and no. I can keep the stand as pretty pure sheep's fescue, but it becomes so thick itself that there is little hope of finding or playing the ball. It might work elsewhere, but our topsoil is too fertile.
The fescue does only tolerate light doses of Round-Up. A half-rate application will scorch it, and I have managed to kill it with full rates.
I can't say about cross-pollination. I haven't seen any that I know of, but that doesn't mean anything.