I think he meant post a comment on YouTube asking the creator how it was done, though for at least one of those, there are two comments over a year old that were never answered, so that may not bear fruit.
Anyway, what you need is a 3d tracking program, such as PFTrack, Boujou, Syntheyes or Motion Tracker. I don’t keep track of Max, but I know Autodesk has bundled Motion Tracker with Maya 2010. Of the rest of that list, Syntheyes is the most affordable, at ~US$500. I have also heard of a freeware solution called Voodoo Tracker, but I haven’t looked into it yet, as I have easy access to PFTrack at school.
The tracking software exports an animated camera that you can import into your 3DS Max project and use to render your CG object. That render is then composited over your video footage with a compositing program such as Nuke, Shake, Fusion, or After Effects.
For more information, try searching for the term matchmoving. VFXTalk.com has a subforum devoted to the topic.