They joined the new venture once GSS finally lost their AOC.
I hear that some earlier leavers (mainly Ops/Engineering) are being sounded out as to their availability. Many of them found other roles after leaving GSS but not all were happy with their new jobs either due to location or employer so are considering this new venture.
A lot of good people were made redundant when GSS lost the BA contract. I hope this new venture gets off the ground (no pun intended) and as many of those guys & girls as possible get jobs at STN again.