Since no one else has responded, I'll chime in. Though I've never hired professional assistance for clearing poison ivy, I had a fairly severe infestation (roughly 1/8 acre of large, mature ivy) that I resolved myself using Roundup's poison ivy specific remover with great success.

Afterwards, I ran the vines through my chipper for compost (the roundup completely dries up the stalk - pretty remarkable).

When it comes to PI I have found you are on your own. Please proceed with caution, we are talking all out warfare. Here is my battle plan:
1. Get disposable, cheap long sleeve/long pants coveralls. No joke. The kind contractors use when crawling under houses. I'll be looking for them soon too. Hoping Harbor Freight has them on Broad St. Let me know if you find them before I do.
2. Always pick a day when you can spend hours in battle to get the most out of each coverall
3. Further protect yourself with washable, waterproof gloves & shoes or boots. You may need to use big rubber bands at your wrists & ankles to be certain none of your skin is exposed during battle
4. Arm yourself with Round Up PI killer, if there is a fast acting or long term formula, it is worth whatever it costs. Walmart or Costco may have the best prices. Get a 1 or 2 gallon sprayer. I got mine at Walmart. Mark some disposable cups w/Sharpie at the level needed to make the solution. You will toss the cup at the end of the day. I do leave any leftover spray in the sprayer and just release the pressure according to directions.
5. Get big heavy duty contractor trash bags. I always get them at Costco. Take only as many as you think you will need for a day's battle.
6. Get some wire flags-the kind you see used to mark underground utilities, etc or small wooden stakes. I bought a small bundle of them at Pleasants
7. You will need a loper & pruning shears
8. When you have all of these items email me & I'll explain how to use them ;)
We shall prevail!