Is data produced by the European Space Agency covered by any such thing as the Freedom of Information Act like in the United States?
That is, are data produced by ESA programs freely available much like they are for NASA programs?
The European Space Agency (ESA) is subject to the Regulations of the European Space Agency. One of these documents is ESA/REG/008 - Rules on Information, Data and Intellectual Property, the goal of which is stated as follows:
The Rules on Information, Data and Intellectual Property, as adopted by Council on 19 December 2001 under the reference ESA/C/CLV/Rules 5 (Final), are designed to promote access to information and data and to cover the use of Intellectual Property resulting from Agency's activities, while fully taking into account the provisions of the Convention and the interests of the Member States and of persons and bodies under their jurisdiction.
Chapter II, Section II, subpoint 1a states:
Access and use to be reserved by the Agency
Information, Data and Intellectual Property resulting from work performed under an Agency contract shall be available to the Agency and Participating States, including Persons and Bodies under their Jurisdiction, free of charge, for the Agency’s Own Requirements in the field of space research and technology and their space applications.
The 24 page document goes on to further detail the exact regulation of release of information, so I would highly recommend reading it if you wish to know more specific rules.