Upstream-Projects are not recognized by Maven-plugin, when defined in a Maven-job by "Build after other projects are build":
Setup "job A" as Freestyle Project
Setup "job B" as Freestyle Project and set "job A" as trigger (Status shows job A as Upstream Project)
Setup "job Maven-B" as Maven Project and set "job A" as trigger (Status does not show any upstream project)
When "job A" is build and finishes, "job B" is triggered, but not "job Maven-B"
You can make "job Maven-B" triggered by "job A" by setting it as a Post-Build-Action in "job A"