IMHO it's all rubbish anyway. It should be down to the individual officer to make sensible choices as to whether they are fit for duty or not bearing in mind their non-performance could impact on the safety of another officer. If you are too tired go home or better still don't come in in the first place. What is non-sensical about it all is that I could go into 'work' at my office and do 8 hours there come home, change (kiss the wife) and go and do 8 hours specialing and this could technically be breaking hte rest period rules but if instead I got up did 8 hours DIY at home and then went to do 8 hours specialing then it would be fine.
The thing is, not everyone makes sensible choices.
I can think of some specials I know who will work 09.00-17.00 then do a night shift 22.00-05.00 then go back to work the next day 09.00-17.00 and do 22.00-05.00 again and work the next day again. While they can get away with the lack of sleep because they are young, but by the third day they must be close to exhaustion and it cant be good for them.
That said im sure we have all policed when we probably shouldnt, at the time of the riots I worked out I did 82 hours work in 6 days. It took me two weeks to properly catch up on sleep, but at the time I felt ok(ish).
My point is, everyone thinks they are ok until someone falls asleep on the way home and and has a smash up.