It is possible! jBPM BPEL would tell you if the referenced WSDL document is unreadable (try setting a bogus value in the attribute location).
I think your partner link type is referencing a port type imported indirectly. There is a known issue about this: BPEL-61. A resolution already exists and will be included in jBPM BPEL 1.0 alpha 4 to be released last Friday :-) (I'm overdue!)