Alright so lets start from the beginning, I got my droid eris around january of last year and after about 4 months had to get a replacement because of a trackball issue. My next replacement was about 8 months after when the power button went out, about 3 days later was because of capacitive buttons and now I have one with a "lifting" screen where dust is actually collecting dust under it. I call verizon and they say because I didnt call when I first got the replacement I have to go to store to make sure I didnt cause it. Alright no problem. I go to the store and they send me a 4th ERIS! Are you serious!? My experience with these "phones" have been so terrible I would rather have my LG voyager back so I dont have to deal with it. The best part is my brother just dropped his and called asurion to do a claim and got his today. Brand new phone with no defects at all, working better than when he had it before.
Your warranty is actually through HTC, Verizon just makes the process a lot simpler by offering in store swaps. The problem with this though is that they will often do an exchange for a customer's phone on something HTC would not cover.
How it works is if the claim is something that HTC is valid (and not user error), they will ship Verizon either a new or factory refurbished device.
If HTC does not accept the claim, then Verizon is left with a broken phone. So they attempt to fix it themselves, with varying degrees of success (though more often then not, it's not horrible. Remember, people rarely post about positive or average experiences).
Now, when a phone is new, a majority of replacements will be HTC replacements, or devices that were returned under the WFG. But as the years go out, those replacements are steadily replaced with Verizon refurbished devices, and when those refurbs are exchanged they are fixed again and put back into the pool.
Since we're almost 2 years out, I'm willing to bet that most of the refurbs out there will be Verizon fixed and not HTC models.
That being said, we did a warranty claim for my dad on his OG droid last month, and I swear they sent him what looked like a brand new phone as a replacement.