Microsoft's General Council, Brad Smith, tweeted that Microsoft asked Google to join the consortium, but Google refused the offer. This certainly puts a little pie in the face of Google, which has consistently accused others of trying to compete using lawsuits rather than innovation. Below is what is allegedly the e-mail showing Google decline the offer, although an e-mail like that could seemingly be faked fairly easily. The e-mail is shown to be from Kent Walker, Google General Counsel.
It'll be interesting to see how Google responds to this.