When I had a pair of Eclectus, they tolerated but were not friendly with a variety of cockatoos and african greys. I could place them nearby on a stand with nothing worse than maintaining about a foot of separation at minimum.
I have a 15 year old eclectus that as of now, tolerates my cockatiel's existence when they're both on me but have not had solo interactions. A young eclectus at my work however is very playful and gets along with most other birds. It really depends on how they are raised. As far as I am aware my boy was rarely or even never around other birds while the younger one at work was raised around all kinds of birds.
Interesting. I don't know how my eclectus feels about other birds, because my other birds--my golden conures and BWP--are very bird-aggressive and I don't dare allow them to have any contact with Peaseley the eclectus. So I know that they hate other birds, but I don't know how Peaseley feels--except probably deservedly afraid of golden conures and pionus.
Just to be clear, having learned about this aggression early on, the aggressors are never allowed access or even proximity to Peaseley.
Our 10 mth old Ecky Sonny thinks he's a rainbow lory as he sits in the trees with them and they fly in the house to feed on the food I put out for them. We have about 4 pairs that come in the house. He will sit next to them and hold his head sideways and down low so as to not threaten them. 50% of his sounds are from them and he knows how to call etc. There's no chance of him finding another Ecky around here in the wild so it's the best he can do. Doesn't get along too well with magpies but can give them the slip if chased. He's allowed out every second day if the weather etc is OK and comes back within an hour now.
Every ekkie is different. I've seen some who get along VERY well with other types of birds. Others? Not so much. But its always important to be mindful of size differences. Any birds either significantly larger or smaller than an ekkie should never be trusted alone with him/her... no matter how well they get along. You just never know, and those beaks can do a lot of damage in a short period of time.