[WillPS]

Analogue cable definitely had rough time shares on the same channel numbers.

ONdigital never seemed to manage it either - they had a few timeshared channels ('UK Style Horizons', 'Discovery K[ids]+W[ings]' etc). They did have ITV Sport Select which borrowed time off another channel when broadcast (I think only a handful of times) but I imagine that was manually reconfigured each time. CBBC/Cbeebies timesharing with different LCNs to Choice/Knowledge was the first daily one I knew of on DTT, and it seemingly involved 5-10 mins of downtime each switch over to do it initially.