It is easy to see why the NDP-Green alliance is doomed to fail.
1) A power hungry NDP leader who will make rookie mistakes........power intoxicates. 
Take his opposition to the Trans Mountain expansion as an example. A political leader cannot directly influence the job of a Career City official who has to make decisions based on set guidelines. (Imagine a City official not giving you a building permit for your house because you voted for a different political party).
2) A Green Party that will feel side-lined by the NDP .
3) A well oiled Liberal party that will make the NDP-Green leaders look like school children!