That start sequence is correct. If we have a tug, we will usually start no.1 on the push. There are actually several possible engine start sequences available on the ATR, but as you mentioned some operators will only use one method, while others leave it to the crew to decide which one to use depending on circumstances.
ATRs can also do a battery cross-start. (I remember doing just that one day in MXP when handlers weren't on stand, and weren't answering the radio either. Only in Italy...)
Cheers
