The Parameterized Trigger Plugin, which the MultiJob Plugin depends on, makes the following environment variables available to future build steps if "Block until the triggered projects finish their builds" is enabled:

• LAST_TRIGGERED_JOB_NAME="Last project started"
• TRIGGERED_BUILD_NUMBER_<project name>="Last build number triggered"
• TRIGGERED_JOB_NAMES="Comma separated list of all triggered projects"
• TRIGGERED_BUILD_NUMBERS_<project name>="Comma separated list of build numbers triggered"
• TRIGGERED_BUILD_RESULT_<project name>="Last triggered build result of project"
• TRIGGERED_BUILD_RESULT_<project name>RUN<build number>="Result of triggered build for build number"
• TRIGGERED_BUILD_RUN_COUNT_project name>="Number of builds triggered for the project"

It would be nice to have these for each phase (prefixed with the phase name)), too. Esp. TRIGGERED_BUILD_NUMBERS is important if artifacts need to copied from the triggered builds.