At the moment Evolution can only handle to subscribe to a drafts- and sent-folder. I request the possibility to subscribe to a trash- and junk/spam-folder, too. 
After a mail exchange on the mailing list I know that especially the trash is handled as a virtual folder and deleting mails means just to mark them and find them in that virtual folder. With junk/spam it seems to be the same. 
But atm I have 2 trash-folder and 2 junk-folder, one of each is a virtual one by evolution and one is a folder my mail service provides.

All in all I would suggest that Evolution should support both ways of handling this. Where the first is that deleting a mail is marking it and find it in a virtual trash and the second one is to move them to a real trash I can subscribe to. Junk/spam can be handled analogue.