These classes still exist and are part of the eunit.junit plugin, which is part of the core.dt feature (Core Development Tools). However, they're not in the standalone JARs, since internally they use some Eclipse components. I could split off the Eclipse-specific bits, however, if that's what you need. Would that work for you?
Sorry for the delay: I didn't receive any notifications regarding your edit :-/.
You can call this operation from anywhere in the EOL file: see all the "transform();" calls in the .eunit file?
Essentially, operation contributors allow you to add methods to an object through Java reflection. If you always return true in the contributesTo, you'll add the method to anything, including the special EolNoType value that is used for context-less calls (e.g. "transform();" is contextless, "a.transform();" is not).