If Siemens was on the Leafs he'd be the next coming of jesus, he was drafted 11th overall just 2 years ago. Hell no the Avs would say yes to this. Is like the Leafs trading Rielly because they see what he can do at the NHL level.
With rumors that Toronto is shopping Phaneuf and that initial negotiations with Franson weren't going so hot, why not try to upgrade at center when dealing from a position of strength? I know they just drafted Gauthier, however Toronto is a rising team with the real ability to make a deep run this year and adding Statsny would only make them better. Supplementing their defensive prospect pool with Siemens and forward prospect pool with Sgarbossa, would also be a good return for the players they are dealing.
Reasoning for Colorado:
It's obvious that Colorado needs to improve their defensive corps and adding Phaenuf and Franson when dealing from a position of strength would be a smart move. It allows Johnson to play his natural game rather than trying to do it all himself, and would allow O'Reilly to play his natural position at center rather than moving him to the wing.