It's great that this letter is signed by 'transsexual people' and not 'transsexual women' even though all the signatories' names are more traditionally associated with the female sex. It's great that the letter refers to us simply and unequivocally as women and states that we are oppressed because of our sex, and not some metaphysical gender identity.
While I wholeheartedly support this letter and am grateful to all who signed, I am wary that it may be used by some in an attempt to leverage female socialisation. Some may have misinterpreted 'We seek to find common cause with women against male violence' as 'let us in your lavs,' when that was clearly not the intention.
We had an 'honour system' (except it never was because women were never asked, it was a 'put up with it and don't make a fuss, it doesn't happen often' system). Lots of women have never been comfortable with it. Of course nobody shouted 'ooh look it's a geezer' because of female socialisation, which includes both the polite centring of male needs and the constant risk assessment we all perform in the interests of self-preservation. You won't have noticed the women who just quietly left. You won't have noticed those that stayed standing, fully dressed, in their cubicles until they were sure you had left. You have no concept of women only space because as soon as you enter, it's a mixed sex space.
Women don't need an excuse in order to object to sharing toilets with males. Whether we have a history of sexual assault, religious or cultural rules we have to follow, or neither, we are all entitled to not only safety but also privacy and dignity. Thinking that as long as we keep out the males who might hit or rape us then everything's fine shows a very low regard for women, what we are worth, what rights we deserve.
It's not women's job to sort out where everybody goes for a piss. Lots of us here are mums, but we're not your mum. You do the work to come up with solutions that meet your needs and don't crap on women and I will support your efforts, although I'm with Spartacus here, I will spend more energy on campaigning for more Changing Places because there are people who cannot physically use any toilet.
Third spaces are the obvious solution but not good enough for some apparently. If the trans lobby got behind this idea you'd have a commitment to providing third spaces tomorrow. Until a year or so ago, the trans lobby could ask for the moon on a stick and get it in short order. The political landscape has changed somewhat since then, thanks to the huge uprising in women's resistance. Right now, a suggestion for something that made life easier for trans people and didn't piss off women should be hugely popular. Everyone (aside from the 'aggy kids') is sick of this impasse. Yes it's expensive but there appears to be plenty of money sloshing about for the likes of Stonewall, Gires etc. See if you can divert it.
If there are genuine problems with the third space solution then really it's up to trans people to come up with other suggestions (cf. 'we're not your mum') I have no interest in being nagged and cajoled into giving up my boundaries in an elaborate game of 'yes, but where do I pee??'
Toilets are the least of these issues, obviously. Maybe we should be starting with the most important and urgent contexts. I seem to remember Women In Prison have tentatively suggested third spaces as a solution to dire situation in prisons.