The evidence was the (since debunked) claim that 75% of drivers at one depot were isolating either due to having the virus or having been in prolonged close contact with someone who went on to test positive for it (from symptoms that developed) in the following 48 hours, as there is simply no other reasonable explanation that could explain such a high incidence of cases given the typical level of workplace interaction between drivers and the wider local infection rate.
No the issue was 25% productive establishement - this can be due to sickness, self-isolation but also there are Covid related reasons such as a backlog of drivers awaiting training. This is true for all TOCs. There can also be outbreaks in specific areas evn where wider infection late is low; many factories and universities have had this problem so its totally reasonable. Although you could ask a question as to whether social distancing measures are adequate in mess rooms and/or being adhered to - but still I doubt it - its highly cynical to suggest these issues aren't ultimately related to Covid at exactly the same time a timetable increase was mandated.
