I can see Ottawa making this trade.
I can see Blake Coleman a good fit for the Sens.

Coleman would be a great fit for the Sens. But he is already a great fit for the Flames. This offer does not interest Calgary at all

Garbage offer for a player the Flames won't trade unless they get a terrific offer.

Unlike most people here I don't see why the sens do this. Coleman is having a good season, actually a career year at 32. It's awesome to see but how sustainable is it as he gets to 33, 34, 35? Signed for 3 more seasons after this at 2 mil more than Joseph who is just as productive. He will regress hard next year and I bet the flames will be complaining about that 4.9m for a 33 y.o 3rd liner.
Sorry but I'll take my chances with a younger, faster 2m less player and less term. Sens want some vet depth, try free agency. They don't need to make these expensive asset trades

"Garbage offer" is a HUGE stretch.