As far as I'm aware BASSA are aware of the proposed changes in FDL for flight crew, having read through the proposal it's my understanding that it will affect the flight crew hours more than the cabin crew who's scheme already does most of whats being proposed. 7.5hrs minimum rest not withstanding.
Cabin crew have only had the 900hr restriction for 5 years or so, before this there was no annual restriction on hours, I can only speak for long haul at BA, but cabin crew would regularly do 1200 hours per annum, to the point one of our recent managers complained on a forum chat , and I quote,
"We pay for 1200hrs and only get 900hrs from our cabin crew now".
The other side of the coin is that the cabin crew themselves don't like the 900 hour rule because if they are full time they get up to 3 weeks a year grounded due to 900hrs. thats viewed as a wasted opportunity to earn.
Regardless of where you stand, there is no denying the massive rift between the flight crew and cabin crew at the moment (not a pop just reality). The cabin crew at BA are just not inclined to listen to flight crew calls for solidarity in great numbers regardless of the result of inaction.
Possibly a sad state to be in, but it's the reality of recent times.