Betham, a personal trainer, promised more fireworks.
Promoter Dean Lonergan said Scott-Young had vowed to "knock Monty's head off".
Jonah Lomu will lead a rugby union line-up squaring off against a rugby league team led by former Australian dual international Wendell Sailor.
Former All Blacks Troy Flavell, Carlos Spencer and Christian Cullen are in the rugby team and Kiwis player Issac Luke and former stars Awen Guttenbeil, Joe Vagana and Jerry Seuseu are in the league team.
Warriors star Manu Vatuvei is a possible opponent for Lomu, at the Trusts Stadium event in Waitakere on December 3.
The event will raise money for the Prostate Cancer Foundation of New Zealand and is being promoted by Lonergan and Duco's David Higgins.