According to one urologist named Dudley Danoff, from a MEL Magazine article, it is not something that happens. So, while this is just one doctor’s report over a lifetime of patients, this would seem to indicate ejaculation during a prostate exam is exceedingly rare. Hope this helps. Cheers!
If you have time for a podcast, ScienceVS has done two episodes on trans people with well researched citations. The more recent episode looks specifically at the issue of bullying and negative trans experience. Hope this helps. Cheers!