It is becoming a fairly normal procedure to collect semen from testicles of a bull that has recently died. I know of one case, where a herd bull died suddenly and the owner cut off his testicles and headed for the vet college, where they successfully froze over 300 straws of semen.
A few years ago, when my herd bull Saskvalley Pioneer 126P died of a massive heart attack, I spoke with the head of the reproductive physiology department at the Vet college in Saskatoon, SK. He recommended that I cut his testicles off and put them in ice in a cooler and take them there. It was a 250 mile trip, but he was fairly certain he could obtain good semen from them even after that long a drive. I decided that seeing we had collected a fair quantity of semen already that we probably would be OK.
I have heard of a few others who have done the same thing.