Cornelius is right on. The only thing that transfers to you ATP from your commercial is the aircraft type, category and class that you do the ride in. So if you had a type in a 717 and did your ATP in a Lear 35, you would have an ATP Multi-engine land with a Lear 35 type and a Commercial Multi/single land with a 717 type.
Gubernator is correct. If Corky obtains a 717 type rating on the commercial certificate, it will automatically be given ATP privileges upon passing the ATP practical test in the same category and class of aircraft. It is NOT necessary to pass a checkride in that particular type.
For example, if a pilot holds a 717 type on his commercial certificate, but passes the ATP checkride in a 737, the ATP will show type ratings for both the 717 and 737. That pilot will hold ATP privileges in both the 717 and 737. This occurs automatically, without additional paperwork or a separate request.
14 CFR 61.157(d):
"Upgrading type ratings. Any type rating(s) on the pilot certificate of an applicant who successfully completes an airline transport pilot practical test shall be included on the airline transport pilot certificate with the privileges and limitations of the airline transport pilot certificate, provided the applicant passes the practical test in the same category and class of aircraft for which the applicant holds the type rating(s). However, if a type rating for that category and class of aircraft on the superseded pilot certificate is limited to VFR, that limitation shall be carried forward to the person's airline transport pilot certificate level."
Use some caution with the FAQ site. Those who maintain it are very kowledgable, but the site is largely opinion, and represents no legal stance on the subject. Otherwise, it's a handy reference, so long as the material is taken with a grain of salt.
maybe Ksu and Corneilus were confused about "Catagory" (airplane, rotorcraft, airship) and class (MEL, SEL) gubernator's reference is right on the mark and easy to read, unlike a lot of CFR. Besides being on the FAQ list, if I recall correctly this question is asked about 6 different ways on the ATP written.
Your type rating will carry forward to your ATP. Your type rating is just that, a type rating. It does not relate to the privileges you may exercise as a pilot relative to pay or command of a 121 airliner.
The PTS for ATP and type rating are the same.
For that reason, then, Corky, why don't you wait and do both at the same time? Your profile shows you're nearly there anyway. Two birds with one stone.
And, further to Avbug's comment, in the old (golden?) days of airlines, FOs flew for years with just their Commercial certificates. ATPs were comparatively rare. Virtually no one got the certificate on their own. When FOs finally got their captain upgrade, they took their ATP ride with their airline.
I remember about that about fifteen years ago the commuters were hiring with 1500 total and 500 multi. Having just the ATP written, even that recently, gave you an advantage. Then, more and more people started showing up with the ATP and they started making the ATP a requirement.
I hear ya. I am ok Total time but I lack a couple hundred cross country. I'm halfway through the training and my employer (Boeing) had a slot to put me through now. Maybe I can do the ATP in the sim later!