I've worked in hardcore industrial areas, and believe me...LOTS of these things are connected to phone lines...a couple even to the internet (got help us all).

I know quite a few use PCAnywhere so that manufacturers can dial up and troubleshoot without flying someone half way across the country.

Luckily when we installed one of the newer machines and they told me they wanted to have a PC connected to the machine via serial and get on our LAN and out across the net...I nearly had a heart attack and bitched up a storm till they said no way...I just couldn't imagine someone compromising our network because they put some wierd factory equipment on the net.