|Sort of - depends what you mean(!)|
Typically, a proper 16:9 TV (ie. the tube is wider than normal) can switch to 16:9 mode when receiving a 16:9 signal. Some can also be manually switched to 16:9. Some 'normal' (4:3) TVs have a 16:9 button, so that the image is squashed vertically, giving the same 16:9 effect.
Almost all normal (4:3) or 16:9 TVs can receive a standard composite video signal, and so therefore you can connect our scan convertor units (with composite video outputs) to them. However, a 16:9 TV will normally just show you the normal-sized (4:3) image from this with the left and right-hand borders remaining blank. You might be able to press the 16:9 button to stretch it out horizontally, but that's up to the TV - it won't happen automatically as it might with a satellite or aerial signal.
For our video scalers (C2-4000, C2-5000 and C2-7000 series) there is an ability to squeeze and stretch the video image as you wish (Advanced Aspect ratio is active). This gives you complete freedom for image sizing, and even shows you the current H:V ratio.