scroggs ...
Speaking as an ops / ATC Cell bod, the problem we have with these regs, and incorporating them into CFPs is that the majority of them are tactically introduced as opposed to notam'd or forecast. Factors affecting their usage could be as diverse as staff shortages, wx, aircraft demand, radar unserviceabillities etc etc
It depends a lot on how much time in advance your CFP is produced from your report time as to when the info on ATC tactical regulations is available.
the easiest option would be to increase your 'holding fuel' allowance, but again that depends on company SOPs etc etc.
But from a flight planning dept perspective, it's not easy to give you accurate info to that degree unfortunately.