I signed an email -Bean PE after I got my results. It was to a friend, and we were discussing mountain biking.
I have not updated my work email signature and don't plan to as they have no intention of promoting me (or anyone else) to a PE position and as such, they will not benefit from it.
I have a different view I guess, just because the company will not benefit or promote you to a PE position doesnt mean you can't or shouldn't use the initials behind your name. The PE represents professional credentials you earned not a position your employer hands to you like in a promotion. I say you are promoting yourself and your own professional developement at the same time you are working for your current employer. While you may not be signing/sealing drawings everyday you have worked hard and earned the right to put the letters behind your name. Use if to market youself and network with potential employers, clients, colleagues with whom you may work with/for someday in the future.