Check out the "retention" thread in this forum. Lots of info there, although primarily for existing customers, ther eis info on new as well.
http://www.digitalhome.ca/forum/showthread.php?t=48593
The short answer is "yes" there are deals to match competitors.
The most common one, and you can check the bell web site as it is usually there, is a free HD PVR rental for a year, along with 6 months free HD programming.
Mentioning a competitors deal is never a waste of time.
There are likely many options for you to play around with and find one good for you. You mention 50% off, which is good if you plan on buying the equipment. Most people take the free rental as that way a year from now you can re-evaluate and see what the best deal is with no cash outlay. Possibly get new receiver models by that time too.