Ummm... It's called CORNED beef
Yes, it is corned. I put the contents of the packet into a tea ball and toss it into the crock pot with the corned beef if I'm cooking it that way. For pastrami you could grind it and include it in your rub or just toss it.
BTW, if you haven't researched this yet I recommend Thirdeye's site...
I always soak store bought corned beef in fresh water for at least 24 hours, changing the water two or three times, to leach out some of the salt.