Having read the past 50 pages or so, I thought I would offer my tuppence-worth. Whatever the reason for the lost SSR/comms, it would appear to me that a major causal factor was the lack of robust ATM procedures. This accident occured with CAS, a known environment. If ATC did not know what the Legacy was doing, they were no longer able to provide IFR separation. It appears to me that somewhere along the line, ATC has assumed instead of knowing.