CRM comes with web services (depending on the version also with odata) for interfacing. Same applies for Project Server (on-prem: PSI / Project online: CSOM). Therefor an interface between those two can be implemented. You could either custom code or use a standard product for this. The company I work for (Campana & Schott) has a product on the market with which we can do this type of integration (CS Connect – http://www.campana-schott.com/en/technologies/cs-connect). One use case you could for example implement is that you track leads inside of CRM; once a certain probability for the lead has been reached a project in Project Server will be created and key information will be transferred into Project Server. Therefor also the scenario mentioned by you should be possible to implement. Please let me know should you need further information on this.