The Red Gold Blue and Green lines work great although I haven't been on the Orange line buses yet. But we need something to link up OC to the Metro Rail system. If Irvine gets light rail, and it connects to Santa Ana and Anaheim then it could eventually link up to the LA system.
Metrolink (Amtrak) trains do go to Anaheim but unless they alter the course so it goes to Downtown Disney, or get an Anaheim light rail link working, I dont see people using it to get to the Mouse.
If it linked up the stadiums and theme parks it could work to get people on Metrolink, which serves everything from Palmdale to Ontario to Ventura to San Diego. I don't conjure him up often but I think Walt Disney would LOVE a rail link up for the Disneyland Resort.