This page from GCHQ’s internal GCWiki, dated 27 May 2009 describes a system for querying mobile phone information acquired during port stops: see the Intercept article Airport Police Demanded An Activist’s Passwords. He Refused. Now He Faces Prison In The UK, 23 September 2017.
This document dated 20 January 2011 provides the research agenda for a joint NSA/GCHQ group tasked with developing “a sound understanding of the threat that encryption brings to our ability to do target discovery/development as well as devising mitigations”: see the Der Spiegel story Prying Eyes: Inside the NSA’s War on Internet Security, 28 December 2014.
This page from GCHQ’s internal GCWiki, last edited in May 2012, provides background information on the agency’s “internet buffer business capability”: see the Der Spiegel article The NSA in Germany: Snowden’s Documents Available for Download, 18 June 2014.
This May 2012 memo from the NSA’s International Crime and Narcotics division describes the operation of the MYSTIC system in the Bahamas and another, unnamed, country: see the Intercept article Data Pirates of the Caribbean: The NSA Is Recording Every Cell Phone Call in the Bahamas, 19 May 2014.