Would be about like the AM and NH carriers descending from 1680. I would venture to say it wouldn't be as wide spread. 878 and Foresight have made a big impact on the breed but 1680 was born 20 years ago and is found in a lot of the performance pedigrees today. 878 was born 8 years later and is found, in my opinion, in herds that focus on maternal, functional cattle that don't want to sacrifice performance. I would venture to say that due to embryo transfer being adopted by performance breeders sooner than functional breeders, that 1680 has a larger population of offspring and descendants.
Doesn't really matter what the fallout would have been since they have both tested negative.