DTX is used during dedicated mode, on non-BCCH TRX.
C1 and C2 are used by MS’s to (re)select a cell : it is performed in idle mode, on the BCCH TRX.
There is no interaction between the two : the MS are using the RXLEV ‘FULL’ because they don’t wait to measure just some special timeslots (however it shouldn’t be called ‘full’ : it is just a level measured on a signal, not on specific timeslots – as far as i think)
Don’t forget the MS’ are measuring the BCCH of their serving cell + all the other frequencies in their bands…)