An MR Faraday cage attenuates the RF signal about 100db (according to the engineer who built it). Phones work as long as the door is open 1mm or so. Blue tooth works through the cage just fine. Wifi doesn't work very well anywhere near the cage.

MR scanners get nice pictures with the scan door open, but the if the scanner next door has its door open (so 2x scanners running with door open), images are wrecked.

Also, the coastguard sends you grumpy letters if you leave the door open and scan (at 3T).