Just to correct one point, Mixed Fleet was never intended be a non-unionised workforce per se, but a separate bargaining unit which is what it is under Unite. Put another way, you could ask why it has taken two years for Unite to gain recognition. The chances of Mixed Fleet integrating into EF/WW are next to NIL.
And BASSA's membership numbers are an irrelevance, by their own admission in their updates they have been sidelined.
Anyway, it's good that negotiations are ongoing. What is needed at these times are cool-heads, creativity and intellect not bluster and bravado.