
I don't chink it is likely to happen much here, as AI is not allowed for resident dogs, and after expensive AI for imported semen no-one is going to want to risk the natural studs semen being more lively and fertilising all the available eggs.
Also from a breeders point of view it would mean a logistical nightmare, how to co-ordinate travel to two studs, pay two stud fees, with the majority of 'pet' puppy buyers caring not one iota which stud sired their pup, so not a lot of point going to the extra expense.
After all how many breeders would want to keep two half sibling pups, as arguably you would want one from each sire.
Statistically also it would only be worth doing in breeds that regularly have large litters of more than 8 pups to be fairly likely to get pups of both sexes by both studs, as the thought might be to minimise the number of large litters a bitch has to rear..