The Rottweiler has had his own personal kitten (we named him 'Toy' because the Rottie would play with him when he was a wee thing. Kitten was a midget, head grew, body didn't and we didn't expect him to live. He grew and grew and his body caught up with his head and he is a gorgeous registered Himalayan adult male with Paul Newman eyes! LOL). The Rottweiler, named Tonka, is fine with cats (his own) and likes them just fine, doesn't chase or pester, but he doesn't like ANY strange animals invading his space - not wild about people who invade his space although on neutral territory he is fine with everyone and everything. He has a particular aversion to UPS trucks and we have no idea why. Just parks himself in the middle of the drive and puffs himself up so he looks bigger (not necessary, he's big enough at 139 as it is!) and refuses to budge.
I would not consider for one moment going to the time, trouble or expensive of having someone else's cat neutered. I would seriously consider humane traps and a trip to the local SPCA (it is NOT a no-kill facility).
I've spent hours on the web searching for products and advice, the best I came up with was UofOhio or OhioUniversity newsletter on the subject. May try that. Something called Kennel Odor Eliminator which is industrial/commercial strength. Also something called CAT-OFF that you get from the vet, probably pricey.
I'm off to try a protein eater on it since we've had a few dry days and it should soak in. Will use a stronger than recommended dosage and see how it works.