What equipment are you interested in? If you're talking about selling your equipment, you should probably not count on allowing it to phone home, especially not without good documentation (purpose, destination, port, configurable timing). Somebody will put your device on a network from which it is not allowed to reach the internet.
If you're buying equipment, I can't speak from experience, but I'm sure there's plenty of crap out there that plays by whatever rules the developers felt was convenient. Big buyers with clout probably have a slightly easier time getting more strictly controlled stuff.
My personal experience is that I work for a company that sells appliances. They phone home only for software updates, but the user has to configure the time and the destination (update servers are chainable) and may pass through an http proxy. If they don't like that method, they can download the packages manually and upload them to the appliance through the web interface or burn them to cd. We sell mostly to fairly large organizations.