"Reforming the GRA has nothing to do with trans people accessing bathrooms. That's a right protected under the Equality Act."
Strictly speaking, correct. The Equality Act protects trans people from discrimination. So a male person may not be prevented from accessing the men's 'bathroom' because of how he presents. According to the EA, Miranda, Caitlin and Pips have the right to access men's facilities, and preventing this would be a hate crime. Similarly, Buck and Steven's right to access female facilities is protected by the EA.
Somehow I don't think this is what the BBC intends us to understand from that statement.
And what's with this "bathrooms", anyway? We are not Americans! Use the correct words for clarity. It's pussyfooting around 'rude' words like SEX that is partly responsible for the pervasive creep of this mess. Bathrooms are private, domestic spaces, not a place where people are vulnerable among strangers. Saying bathroom instead of toilet, or facilities, or services, is Rohypnol.