I'm having some mvel expressions that evaluate differently in different places; in once case I get different answers, in the other case, the expression works in one and fails in the other.

Background: I have a configuration A that triggers a build of configuration B and copies back files from B.

Problem 1)
I need to provide the full path to B's workspace. (Since the implied workspace for copying back seems to be A's.) When I use ${system.getConfiguration("/path/b").getWorkspaceDir()} in the trigger step, it does not yield B's workspace (it appears to yield A's workspace). However, it yields B's workspace when I use it in a plain build step (running a shell and printing the value).

Problem 2)
I was originally trying to get B to run on the same node as A. I passed A's name and port as a parameter: ${current.getNode().getHostName()}:${current.getNode().getPort()}
This failed, with a message about mvel not able to evaluate the expression. If I create a regular build step and use that exact same expression, it evaluates fine.

Am I doing something wrong? Is there something special about the environment in a trigger step when these are evaluated?