Well, Mark has started this thread with the question "What was the least likely country that carried CT40? My guess is either Zambia or Uganda... I mentioned Uganda and Zambia... because they actually did carry CT40!"
If you wonder where to hear it, Casey mentioned one of those on CT40 broadcast of October 18, 1997 - Radio Sanyu 88.2 FM Kampala, Uganda during one of station mentions.
Just to move on with another two stations: on Casey's Top 40 of December 15, 1990, the last regular weekly show before the year-end Top 100 countdown Casey mentioned 100.5 FM Turin, Italy and 107.85 Munich, Germany.
"Radio Maximum in Moscow, Russia was again mentioned on the show of October 16, 1993 again guest hosted by David Perry" - Correct! Radio Maximum started broadcasting Casey's TOP 40 in the end on 1992 in Moscow and then in St. Petersburg. Before that time there was "Russian version" of the countdown called USA TOP 20. The same Westwood One team worked on the program. Also VOA europe was broadcasting CT40 among different sities in Russia in 1993-1995
Just to put something new here, there are few more foreign station mentions on Casey's Top 40 show of May 4, 1991:
Casey, while introing Robert Palmer's medley of "Mercy Mercy Me/I Want You" slipping 11 notches to #28, mentions Radio Kokkola 96.7, Kokkola, Finland, and when introing Hi-Five's "I Like The Way" moving up two to #9 to become their first Pop Top 10, Casey closes the station mentions with the Olympic Action Radio 106.7 FM, Athens, Greece.