I've moved your post to VirusScan Other for better attention.
No, they won't talk to the epo4.5 server- you will need to upgrade their agent to at least v4.0 for Mac (it says this in the install guide) for them to receive policies.
And then its recommended to install the latest software (if the OSx version supports it) for Macs which is McAfee security for Mac 1.0.
Check out the "Installing McAfee agent" in the product guide to see how to get the sh file needed to install on a Mac.
Remember to check in the latest version of the agents first into ePO.