You might not have RTFA, but the Greeks are NOT complaining about the filming per se, but they want to be reassured that the data collected will be protected in accordance with current European law. For example, police recordings are protected or, at least, they have made a case for how they will protect the data which has satisfied the appropriate legal bodies. However, Google has not convinced the Greek authorities that it will provide adequate protection of its data.
Now this might not worry you. But in Europe, collecting the data is only the start of it. Personal data (and that includes identities, addresses, personal habits and traits, a person's car details etc), if stored on computers, can be collected only for a specific purpose and must then be protected from unauthorised use i.e. from being used for any other purpose. Google must state what they intend the authorised use to be (which they have) and then state how they intend to protect the data from any other unauthorised usage (which they haven't yet done). How will they prevent criminals from accessing the data for unauthorised purposes? The claim that it is all in the public domain is a bit of a red herring - criminals don't usually have such a mass of data at their fingertips and, in any event, it is for Google to show how they will comply with the current law not to argue the case for why the current law should be changed. How will they prevent individuals from accessing the data for a purpose other than that intended by Google?
I don't criticise Greece for its actions but I do criticise many other European countries which have simply ignored European law and allowed the data collection to continue. Google might be able to comply with the current legislation and, if they can, they will be allowed to continue.