www.shamsports.com, the Bulls appear to be about $4M over the cap this year. They have never once ever paid luxury tax before.
Without any options picked up for next year, they already have a payroll of $77.9M and even if the luxury tax goes up to $5M, they would be above the cap. So they could be hit with the repeater tax.
The Bulls have the amnesty clause at their disposal but I'm not sure if they would be willing to just amnesty Boozer without getting any kind of asset for him (one can argue that Bargnani is not an asset, but others may feel differently in the league). Outside of Boozer who can they amnesty that would get them below the luxury tax and still have a competitive team? I believe their only amnesty candidates are Noah, Boozer, Deng, and Korver, and I don't think the Bulls would be willing to amnesty any one of those other guys.
I do think if the next Toronto GM pursued this deal it would be done. But I'm not sure if the Toronto brass would want Boozer on the team, as then they'd be dipping into luxury tax, and is that worth it for a team just scrambling to make it into the playoffs?