Looks like the A321's will be making Trans Tasman flights from Christchurch however just seasonally?
From 1 July - 26 October most Christchurch-Brisbane flights will be operated by the A321's however this appears to have come at a reduction in services and seats.
Currently, there are 10 A320 flights (A320 168 seats = 1680 seats in each direction) this will reduce to 7 A321 flights per week (A321 214 seats = 1498 seats in each direction).
Christchurch to Sydney will also see the occasional A321 on a Tuesday through October but nothing long term yet.