In addition to the World Tour, DiRT 2 will come complete with full online functionality that will be core to the overall experience, with head-to-head competitive online play and new social features to engage the racing community. Prepare for mud, gravel, dust and dirt too in DiRT 2, coming 2009.

It sounds like you'll at least have a head-to-head online mode that will allow real-time races but it still might be a little too early to tell.  Maybe E3 will shed some more light.