I've determined this isn't bearing any weight, but what about as a lateral member?
There's no obvious reason to think that those would be structural from where I'm sitting. Neither end connects to anything that would require lateral bracing under normal circumstances. Were it my house I'd feel comfortable removing them. 

Those pillars are probably fiberglass, not "plaster". I'd try to salvage them and put them up for local sale. You might get a couple hundred bucks for them.