Temples are probably going to be the least circumspect in their
activities unless it is for an evil deity. In that case the temple
will be very secretive about their dealings.

In general Temples will be the most open, but lets look at our own
Vatican during the Middle Ages and Renaissance. Loads of political
intrigue was going on there that the people didn't know about. You
also might want to note on this line that most people then (and in a
BR campaign) are NOT literate, or barely so. So messages travel
mainly by word-of-mouth. I would argue then, that most actions aside
from a Temple contesting another's holdings are probably known only to
those directly involved; an evil or neutral Temple would possible even
be an exception here.

Guilds not be secretive? Probably 90% of a guilds actions are of such
a nature. Do you think a guild cares if their "Espionage" action is
hush-hush? You bet. This is not a given though. The Guilder should
be clever about how he carries out his actions and he should be very
explicit in his explanation to the GM. Anything less would leave the
uncautious Guilder open to discovery, repraisal and all sorts of
nastiness (a lot of fun for the GM) - not to mention the reputation as
a careless theif that he will now carry!

Don't forget, the taking over of anothers holdings is not simply the
act of buying stock in the territory where other Guild's holding is.
Especially in the Guild example, the opposing guilder is going to:
undersell his own merchandise, possibly use some black-mail tactics
against smaller reps of the others holdings, spread gossip about the
other Guilder, inundate a market with his own "product", or any number
of things that a creative Guilder can think of.

Does that answer the question?

>There was a comparison with todays businesses, where you know if someone is
>purchasing stocks in your company. Unlike our "modern" society, the rulers
>of Cerilia do NOT have to report their dealings to any sort of stock-market

What sort of activities do you see guild or temples doing, that people
arn't going to notice ?