Meh, you act like police boxes aren't common anymore, next thing you'll tell me British men are all portly with chopburns and huge mustaches, and drive cars instead of horse pulled buggies, and that "Tally Ho!" and "God Save The queen" are not the most frequently words your likely to hear on an average street....
All joking aside, I have wondered why they keep using the whole "Police Box" thing even in the 2005 series. I can understand it being iconic and all, but after a certain point you have to wonder, I mean "Star Trek" updated their technology to com badges and such when they did most of the later series due to the communictors they had in TOS being a joke given how real tech had progressed.
I'm not a huge Doctor Who fan (always meaning to see more of it) but I'm pretty sure I've seen him turn it into other things. I'd imagine in visiting the modern era he'd want to say disguise it as a port-a-potty with a locked door and out of service sign or something. Given the Doctor's general insanity I could actually see him going overboard with "olfactory repellent" for a security system.