XI in SRM, CRM, MDM

Hello. I am trying to clarify when a customer must buy XI (3.0) as a central HUB. I understand that SAP is building integration scenarios and mappings in XI 3.0 so companies may want this. I also undertand that SRM and CRM come with its own Integration Engine in order to communicate with other mySAP components. This does not entail configuring XI 3.0. Can somebody please confirm that:

1) for CRM and SRM, which comes with integration engines for SAP to SAP communication, XI 3.0 is not required. XI 3.0 is required only if you to create new integration scenarios, in which case you can also use Tibco or Webmethods if that is the EAI platform of choice.

2) You do not need XI 3.0 to generate a proxy, it could be done with WAS.

3) For MDM, you must buy XI 3.0.

thanks....