As the ad says, "We're all adults here".
While social stigma has just about equated smoking with stomping on a puppy, there are still a huge number of people that smoke, and smoke happily.
Granted, it may not be healthy, but neither is eating a cheeseburger and you don't see people sneering when someone buys a chunk of cheddar at the supermarket. The media hype against smoking has become its own self sustaining beast. Whether or not someone smokes is their own decision. As long as they smoke in a sensible and sensitive manner (i.e. not in a closed space with other people or where other people may be bothered by the smell) then who are we to pass judgement on them?
E-cigs are both a means to quit smoking and also a convenient alternative to conventional cigarettes. They dispense nicotine and water vapor, and generally the only odor they produce is that of the scent they are infused with. So what if people see you using one? If someone complains that they saw you "smoking" in an ambulance, just tell them that it was only water vapor being exhaled.
And any employer who thinks that E-cigs are a "tobacco product" simply needs to be educated as to the real purpose behind them. Talk with your boss and explain that the product you are using doesn't produce a strong odor or have the same carcinogenic properties as real tobacco. Tell them that it is a way to get a nicotine fix without the typical stench. And if they still don't want you to be seen doing it in the ambulance, then just capitulate and choose to use an E-cig when you have a chance to step away for a moment.
Honestly though, we're all adults here. Don't go running off to tattle or get a cancer screening whenever you pass a smoker on the street. That McMuffin or 'quad extra-hot no-foam latte' are just as hard on your heart as a cigarette is.