I get why they've called it that in terms of it being for corporates, but I find it so apt that they've openly replaced 'sex' (as in Sex and the City) with 'trans' in the name.
Like many of these CSR-focussed groups, they will likely be funded by corporates offering them venue space, refreshments, employee speakers for events, other corporate resources (printing, office space, etc etc) for free under their HR/Diversity budgets (or under no budget for some resources of employees just use them).
It's easy to operate these kinds of things on non-funded basis with no actual money involved as corporates provide all the necessary infrastructure and resources for campaigns/events, etc.
Corporates prefer it that way too, as it's all off-book and doesn't need to go through any formal approvals process. I know that sounds dodgy as hell, but regardless of ethics/corporate transparency issues, it happens everywhere and is considered pretty standard practice for diversity initiatives in the city.