Going live on the railway means the date the wires would be considered by staff to be live and therefore certain rules would apply. It doesn't mean the wires are actually live nor that services will run over them.
Keep in mind that the date given was from here (likely where Rail got it from, certainly copied posts off here before) from a rail employee who like got his notice through stating the wires would be live from this date once they are live, you still need to test which takes a few weeks.
Id be very surprised if early Feb we have passenger carrying 319s.
I remember at the same stage a month before phase 1 was to go live people were saying there was months more work to do and it did miraculously become operational. Those last few jobs like doing a jigsaw it can all come together quickly at the end.
Phase one took nearly a year to actually complete after trains ran. Don't assume just because trains can take power that its all completed.
Phase one switching was not not completed in time which mean the whole new wires were taken as one area rather than smaller sections as planned initially. This meant any issues and power got turned off to the whole thing rather than small sections.
Doesn't mean much to passengers but operationally it means it's hard to deal an incident. No such event took place. And for the record I'm not suggesting unsafe behaviour in any way. Just less flexible system that was designed.