To my fairly ignorant (on this) mind, there are two issues around prisons:
First, the number of men who, taking any sort of dispassionate view of it, look very likely to be using the tactic of identifying as a woman to gain access to the female estate. Many of whom are convicted of crimes against women. They are not trans women, but male sex offenders, who are benefiting from a lack of challenge.
And then 'genuine' (as opposed to well dodgy) trans women who are housed in the female estate, who may, due to their history of offending, still pose a risk to women, and whether effective risk assessment for that risk is happening.
These feel like two separate things, each with their own potential risks/controls/solutions.
I wouldn't want to see a trans women in the male estate, where they would be at real risk. And I don't think that trans woman = offender against women.