One of three UK ports will find out this month if it has been chosen to run a freight ferry service to Norway
Assuming for a moment that a port can find out anything, one port will find out that it has been chosen, not if. All three, presumably, will find out if they have been chosen – I doubt that two of them will be left in ignorance.
However writing 'three UK ports will find out this month whether they have been chosen' does not convey the fact that only one will be chosen, so I simply changed the sentence to:
One of three UK ports will this month be chosen
(And yes, this is all just another excuse to show off the blog's new pullquote/blockquote icon...)