A bus can be reported as detaxed, but a bus can be easily be retaxed should the need arise in a depot, so although the ITT reports that it is detaxed, within days of their source information being issued the bus could be retaxed and on the road. If the bus is back on the road there should be a report on the ITT website that it is retaxed again within the next 4 or 5 days.
I hope this helps, but then again I could have completly lost you on the first word.