Civilization – Do cities received through a trade have any special properties

Looks like this was updated in the June 2011 patch:

[A diplomatic change] Track trades between players and allow that to positively influence relationships (the better the deal for the AI, the stronger the modifier). Particularly useful for bribing a hostile AI.

So it seems these sort of trade agreements do indeed have impact, at least since the patch.

Hover the mouse pointer over the tile you are interested in. After a couple of seconds a popup will appear over the tile, and it will include a line in the form of "owned by England".

So in effect there are two separate "tile information" windows - the one which appears immediately in the bottom-right, and another which appears over the tile itself after hovering. Confusing indeed :)