This is a classic example of where change is needed and a classic example of its too hard, so we won't do it.
Recruitment should be proactive. Look forward to where you may need staff in the future and start planning and training. Generally this is what happens. TOCs do not wait for a Driver to leave, or hand in their notice, then then recruit for a replacement. That would be incredibly stupid, and doesn't happen. Notice periods are a bit of a Red Herring. So, to be honest, is route and traction knowledge. The timetable changes but routes at a Depot don't often change at the same time. Personally, I've had the same route card for about 10yrs at least. Even with all the changes at my Depot, the route card is pretty consistent. A few diversionaries drop off now and then but its just a quick refresher day. Again, that would be a management issue if the Timetable is constantly causing route and traction issues. I fully accept that a TOC can have spikes where there is dramatic change but again, poor planning leads to poor performance. Everyone knew that Covid would have an impact. Some TOCs to steps to protect that future. Some clearly took a different approach.
We have been saying it for years. Rosters are not robust enough. "The Railway" needs to take a dramatic shift away from how things are done and how inflexible they are. This ScotRail debacle really does highlight that change is needed. Give them 10% but with heavy caveats.
Overtime because wages are low is a false economy. If you have the ability to pay the overtime then you are still effectively spending the same money. Low wages means that staff will look elsewhere and potentially leave for a higher wage. This will have a negative impact because you will need to replace them. You are also reliant on those staff. The second they say no, we get to this point and the impact on your business is again, detrimental.
I come from a Retail background. The theory with a lot of their staffing is that you pay less but have more staff. Two staff on 20hr contracts are considered to be better than a single member of staff on 40hrs. One store I worked in had near a hundred members of staff on the books. Our flexibility was through the roof. If anyone went sick you could always find cover. Holidays, training, seasonal work, everything got covered. Another store I worked at only had a handful of staff and we suffered when anyone went sick and I had to go cap in hand trying to get people to work.
Rail staff tend to have high wages so are less incentivised to work overtime but they are also working full time, restricted hours and conditions, subject to all kinds of rules, procedures and policies etc., so trying to get someone in to work can be challenging at times.
It's not easy, but not impossible.