Yes, the names of the panel members and chairs are published on the ERC-website. Please note that the names of the panel members are only published after the evaluation and it will not be disclosed which proposals have been reviewed by which panel members. Furthermore, the panel-members alternate to allow panel members to apply to the ERC calls in alternate years. Thus, panel members for calls 2015 will evaluate for calls 2017 for example and approximately one third of the panel members change from one evaluation procedure to the next.
The names of the external referees are very rarely published.