I believe that CSU (maybe?) did this or does this. There could be others at this point. I'm pretty sure the oocytes have to be harvested within 8 hours of the mare's death, so she would have to either die at the harvesting site, or some expedited shipping of the ovaries (I'm sure with special shipping requirements) would have to take place. The few things to remember: the older the mare the less fertile the oocytes, and getting a pregnacy from just an oocyte is an uphill climb, so you will probably go through several oocytes before getting an actual, viable pregnancy. I'm actually not sure where they are with freezing the oocytes for later use. Most references I can remember used the harvested oocytes immediately.
Dr. Del Vento at Apex Equine worked with CSU to do this several years ago on an older, accomplished WP QH mare. The ovaries were harvested within a few hours of the mare's death and shipped to CSU. I think there were several pregnancies ultimately resulting in the birth of a single foal.
I spoke with CSU about this in 2005, when one of my mares was given very low odds for surviving a colic surgery. They were very informative and I was able to coordinate with the therio vet at the University where she was hospitalized.
Our plan was to remove the ovaries at the time of death and ship them to CSU where they would handle the oocyte recovery and fertilization. Any embryos were to be placed in recipients and I would purchase the mares who checked in foal at 30 days.
I was surprised at how reasonable the estimated expense was. I think it was about the same as a normal ET or possibly even a bit less. The odds of getting a live foal were pretty decent. However, they did tell me that it was good that the mare was fairly young.
My mare made a full recovery, so I can't tell you much else
CSU was great about answering questions and helping me make sure we would have the best chance of success. If I am ever in a similar circumstance, I would not hesitate to contact them.
Molly Malone- from the article that Bent Hickory posted "Oocyte recovery began immediately by carefully scraping the ovaries, then culturing the six oocytes they were able to retrieve and allowing them to mature overnight in an incubator. The next day, five of the six were transferred into a recipient mare from the CSU herd." I read about another case like this where it was a pretty quick process. I'm not sure what all they have and haven't done but it sure would be interesting to know where they're at with all of this.
tuckawayfarm- Yay! Happy story
Sounds like CSU is the place to contact.
Disclaimer: I don't know everything, but I'm sticking to what I know and we'll go from there.