Expense report to Projects flow

Summary: How an employee can create an expense report with project from other BU than his/her home BU.

Content (required):

Here is the scenario in detail : There are three business units A,B and C

The home Business Unit for all the employees is going to be A. But some of the employees need to use Projects from all three Business Units in expense report line. Has someone seen such requirement and how this can be achieved ?

Version (include the version you are using, if applicable):

23A

Code Snippet (add any code snippets that support your topic, if applicable):