I have just uploaded the BRE Pipeline Framework v1.5.1 installer to the CodePlex project page. If you have previously downloaded v1.5 then please uninstall it, download v1.5.1 and install that as it fixes a pretty major bug.
The bug (issue #1767) results in context properties promoted by XML/FF/EDI disassemblers prior to BRE Pipeline Framework components not being available for evaluation in execution policies.
I had actually found this bug during development on v1.5, fixed it, created unit tests, and then broke the code. Unfortunately due to a specific combination of rules in the test policy I was using I was getting a false positive in my tests. Be assured that I have updated my unit tests so that this bug is specifically tested for now.
The cause of this bug warrants an entire new blog post which I will write up in the next few days, and will highlight the difficulties in accessing context properties promoted by out of the box disassembler components in further stages of a pipeline.