In Germany, some sirens are/were mounted in church towers. Unfortunately I don't have any pictures of a siren in a church tower :/
Today many sirens are mounted on masts like in the US and it's getting more and more common. But of course most sirens are (still) standing on houses.
But now I can remember a post in the German siren forum, where someone posted a picture of a HLS 273 on a cell tower. Sirens on a cell tower are very rare in Germany. Here it is:
Credits goes to MiThoTyN, who posted that picture
Today there is an ECN 2400 at the same place

Now itlooks like this:

This is from the user Marcel94.
In Cologne-Niehl is the same situation. The good thing is: it' still active and is tested every first saturday in quarter at 12.00 with all clear-warning-all clear! Look at this:
http://hochleistungssirene.de/index.php ... pic=1#bild
Greets!