Coach Laurie Daley said this week the Blues would make the call on To'o and his sore left hamstring after Saturday morning's training in Homebush.
To'o spent part of the warm-up consulting with Blues physiotherapist Kenny Michalopoulos separately from his teammates.
But the four-time premiership-winning winger ran unencumbered and joined in for the opposed session against the NSW U19s side coached by former Blues forward Josh Jackson.
To'o was briefly substituted out to rest and replaced on the left wing by Wests Tigers winger Luke Laulilii.
But he was seen saying he "feels good" in a conversation with Michalopoulos towards the end of training.
Canterbury winger Jacob Kiraz, who had been on stand-by for an Origin debut, replaced To'o for Thursday's session.
But barring a last-minute disaster, To'o will play at Optus Stadium on Wednesday when the Blues look to seal a series victory with a game in hand.
"He's ready to rock," five-eighth Jarome Luai said prior to Saturday's session.
"He's one of the best wingers to play this game of rugby league. He's a big piece in this puzzle."
Blues right winger Zac Lomax looked forward to playing alongside To'o.
"He's a professional, he gets himself ready and he's played a lot of games here (for NSW)," Lomax said.
"We love having Bizza in the team, he's been an unbelievable asset."
To'o ran for a game-high 225 metres in NSW's 18-6 game-one win and Lomax said the 26-year-old was essential in laying a platform for victory.
"His courage in the back of the field, his effort areas are unbelievable too," Lomax said.
"The best thing for 'Biz' is he wants to get his team forward at the back of the field. That's massive and that's what Origin's about.
"Since I've been able to play with him, that's just the thing that I admire about him, the way that he gets us forward."
Luai reunites with To'o for the first time since the playmaker left Penrith to join Wests Tigers this season.
He said To'o had been his usually energetic self despite the latest injury, which followed two previous hamstring lay-offs this season.
"He's probably even moreso (energetic)," said Luai, called into Blues camp after a calf injury to Mitch Moses this week.
"Because he's not really letting loose at training and stuff, so he's got more energy to bank up and let loose behind cameras and behind closed doors.
"It's always good to have that and to feel that, I haven't been around that for a while. It's good to be with the boys."
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