As far as I was aware Hotline is part of staff travel and is a non contractural benefit. So if staff travel goes so does your Hotline benefit
Hotline is not staff travel, nor is it a staff benefit as you would normally understand. Hotline tickets are low-priced, restricted commercial tickets bought by BA staff for anybody for zero commission. To put it another way, BA uses its employees as unpaid sales agents to sell seats which are unlikely to be sold at higher prices.
So, striking cabin crew will retain their right to buy Hotline tickets, but their usefulness for crew who cannot buy staff travel tickets is limited.