MCPR - Cost added by employee company : connection to PO and SI

Hello to the community members,

I was wondering about a specific scenario in MCPR (Multi Company Project Reporting)

• Employee’s company (supplier) adds cost for flight ticket linked to a job done at customer company. This cost needs to be reflected in the customer company using MCPR 
• Employee add cost on the “project cost reporting” and adds MCPR data 
• If option to create invoice in customer company is used and not voucher option, employee company creates invoice for project transaction and sends it to customer 

Question 1 : should this invoice be sent through MHS?  

Question 2 : Is the process correct till now?  

• Then customer company receives a supplier invoice. 

Question 3 : how is this supplier invoice connected to the cost already registered in the activity through MCPR (cost is already synched in the customer company and needs to be connected to SI?) 

Question 4 : If in the customer company, I have a PO associated to the flight cost, can I connect a PO to the supplier invoice received from employee company ?