1. Create a freestyle project with one string parameter, e.g. "ONE"
2. Create a multijob project with two string parameters, e.g. "ONE" and "TWO".
   1. ONE="TEST ${TWO}"
   2. TWO="TEST"
3. From multijob project call your freestyle project, one time using "trigger/call builds on other project", and one time using "MultiJob phase -> phase jobs"
4. In both cases, select "current build parameters" as a job parameter.

The behavior is different in two cases: for "trigger/call" the parameter TWO won't be passed to the freestyle project, and the variable ONE won't be evaluated to "TEST TEST", while in multyjob phase call, both parameters will be injected, and ONE evaluates to "TEST TEST".