Already failed in the US FTC investigation
"Many of Google's competitors, including a bruised Microsoft, have long complained that the ad giant favours its own services over its rivals' products in web search results"
This was proven to be untrue in the US, and almost certainly fail here too (as otherwise, the EU will look like they are in Microsoft's pocket, as nothing is different this side of the pond).
It's just sour grapes from Microsoft, who suck at most things these days...
What's interesting, is the EU were involved in the US investigation anyway
"The Commission would like to acknowledge the close cooperation in this matter with the European Commission’s Directorate-General for Competition"
So the likelihood of them coming up with a different outcome is slim to none.