Adopt the PACE mnemonic
Probe:- "It's well below minima, Captain - what are your intentions?"
Alert:- "Captain, we can't land off this approach - we need to go around and plan what to do next"
Challenge:- "Captain, what you are proposing is, to my understanding, illegal. Please think again."
Emergency:- "At minima - nothing seen, I have control - going around."
AFAIK, no company has a specific policy on matters like this. You need to give the Captain every opportunity to explain his actions and intentions. If time is tight and other factors dictate getting on the ground in a hurry, there may be little or no time for him to brief you adequately. You do need to know what you're doing, though, otherwise it degrades into a one-man operation.
In your example of a XWC out of limits, ask him if he intends to land or to get as close as he can and abort if there is no lull in the wind - you can prompt him by saying something like "Would you like me to ask for wind checks in the final stages of the approach?"
If you get no response at all from the Captain to your questions or prompts, most operators I have known have a rule that you make two challenges and then take control.
Be aware, of course, that you will need to explain your actions later in the FM's office. Be sure that you
can explain!