The latent period is the time between the start of depolarisation and the start of contraction. I know that the contraction of ventricles starts after sufficient influx of Ca2+ and threshold potential is met. The influx of Ca2+ is at start of Phase 2, so Phase 0 and 1 are included in the latent period.
Comparing to electrocardiogram is not simple, since there is always at least some time lag between the event and the recording. I think there not much sense to compare cellular model events to ECG recordings here.
Which cellular processes does the latent period include?