We currently don't have Restoration Garage in the database.

They restore, buy and sell cars that range from relatively common, such as F-bodies or Mustangs, to rare, such as a Cord 812, to very rare, such as the Roamer, to none-existant, such as the reproduction 1935 Bugatti Aerolith they were building for about five years and just recently completed.

They also do custom modifications, like turning a 1969 Lincoln Continental Mark III into The Car, from the movie of the same name, or restore "Mr. Beep", BP's promotional car they used to promote road safety in schools, which required an entire Ford Zephyr donor car to fix.

Sometimes they just go to car shows and look at very rare cars, but don't buy them.

Should it be added?

I am not sure; we already have a few shows like that...
This one does not even seem to be on IMDb, is it?

It doesn't appear to have an IMDb page yet, but History does have a page on it.

http://www.history.ca/restorationgarage

Should we wait until an IMDb page is made?

I've submitted it to IMDb. It should be added in a few days.

Indeed, better wait that it is on IMDb.
And then, only "interesting" cars should be listed (i.e. those that they restore), not other common recent cars that may be also visible/used.

So, if they just pass by a car at a car show, it doesn't need to be listed, even if it is a really rare car?

If it is an interesting car shown explicitly in the show, it can be listed. What should be avoided is the modern cars not really linked to the restoration thing (except if there is one that they use all the time, for example).

The IMDb page has gone live.

http://www.imdb.com/title/tt3247786/?ref_=fn_al_tt_1