Depends on railroad and location.
Some signage is common among most to all railroads though the look/design on the signs vary.
Other times signage can be unique to a few or one railroad and only used in certain locations.
Example, I note you are from Canada, there's a public resource fo some Conrail signage showing Conrail used a special Whistle Board only in Canada for areas to indicate the whistle could not be used for any reason. I also saw a preview document in a eBay auction for a New York Central crossing sign used only in Canada, specifically Quebec, that was written in French.