If you mean can you receive and process a PPTP connection request from multiple clients masqueraded behind one remote public IP then yes that should work as each connection will have a unique src-port.
For example 10 of your staff are staying in a hotel and all want to connect back to the office via PPTP at the same time - that should work ok.
You must have your PPTP setup to allow each user to receive a unique IP address, or if they all use the same account, select the IP from a pool and ensure multiple logons are enabled in the profile.
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