I think that the AGR has multiple reasons for inviting CCC over either TV or Wanty, with the biggest reason being the international nature of the race. While technically part of the spring classics program, AGR is not a monument nor does it get the same level of attention as the other 'classics'.* They have much to gain by inviting teams with a different base country than Belgium.
So, I think that they wanted to invite Hoogerland (Dutch PR), a young, but attractive team from Belgium (Topsport Vlaanderen) and two other teams with different backgrounds. I think IAM is a logical choice, considering their base and roster. CCC extends the reach to a country that has no ProTour-teams, thus being attractive in that sense. (Technically, the same can be said for IAM, but IAM has other merits (e.g., decent team roster) as well.)
Whether or not you agree with the policy is up to you, but I think the AGR is thinking about the future of the race and that future depends on international attention.
*) I have no intention on revitalizing the debate on the comparative prestige of races. Whether or not you consider AGR as a part of the 'classics' is not of great importance to the argument.