The Fijian-born three quarter joined the All Blacks for last week's training camp in Christchurch, and according to Waikato coach Warren Gatland, will join the squad for their final two games in the Republic.
"Siti was down in Christchurch during the week and I think Graham Henry wanted him to play tonight and next week," ex-Ireland boss Gatland said.
"Then I'm sure there's a chance he'll be included for that South African leg of the series."
Canterbury's Scott Hamilton has been released to make way, with Otago's Nick Evans also joining the training group as cover for the injured Luke McAlister.
Evans and Sivivatu are expected to be released to face each other in the Air New Zealand Cup Pool B game on Saturday, giving each player more game time before flying out.