In the quoted case it would not make a difference if the data storage service was EU owned and controlled because the warrant is asking Microsoft to supply the data.
Microsoft can do that by simply using the normal data retrieval API that data storage service makes available to all its customers. To the data storage service the API call Microsoft will make to get the data the FBI wants is no different than the thousands of other API calls Microsoft is making daily to store and retrieve data.
What using an EU owned and controlled data storage service gets you is that you don't have to worry about non-EU law enforcement getting your data by forcing the data storage service to give it up directly to them.
Microsoft can do that by simply using the normal data retrieval API that data storage service makes available to all its customers. To the data storage service the API call Microsoft will make to get the data the FBI wants is no different than the thousands of other API calls Microsoft is making daily to store and retrieve data.
What using an EU owned and controlled data storage service gets you is that you don't have to worry about non-EU law enforcement getting your data by forcing the data storage service to give it up directly to them.