>The point is: a city is occupied at the beginning of the turn, by some
>player's troops and some BG coexisting troops. At the beginning of the
>movement round, BG declare that they will not coexist anymore, and their
>troops become non-coexisting. Can BG during his move use ornithopters?

IMO, no. A literal interpretation of the rules supports the BG getting
ornithopters by doing this. (Actually, a literal interpretation also does not
rule out coexisting tokens qualifying the BG for ornithopter movement).
However, this then means that the BG can manipulate the use of ornithopters on
many turns, by having a coexisting token in a city, and negotiating with the
current owner to block it as the movement round begins.

The original intent was probably not to allow more than two factions to have
ornithopter movement in any one turn. Since coexistence seems to have been an
add-on by Avalon Hill, and other add-ons by Avalon Hill were sloppily integrated
with the rules set that the original designers submitted, I would argue that the
original intent was different than the conclusion that a literal interpretation
of the rules would give.

>So, in my opinion at the end the point is: should we follow what the
>majority of the groups do, or what a strict interpretation of the rules
>suggest? There is no clear answer to that.

IMO, taking a vote is more likely to discover who is friends with whom, and who
is allied to whom, than it is necessarily to reach the most ideologically
`clean' interpretation. The GM should impose his view of the designer's intent
rather than allow the players to vote.