Possibly. The pic isnt great though and I would be cautious unless you got some close ups of the handle, ferrule and bristles. Unfortunately the 187 is one of the more popular brushes to counterfeit so be really careful with ebay if you are after one of these.
If you click on the photo you can see the grooves are very pronounced, the bristles aren't that straight, and the metal part don't 'funnel' as much IMO. These are traits of counterfeit brushes.
I know what you mean - before i came to this site i knew sweet FA about counterfeit MAC, and i still have alot to learn. LE items almost always stump me, and lip products above all else...
I dont know what kind of crap i would be putting on my face without certain MAC enthusiasts on here!
Looks very much like the brush I got from Ebay and that one was a fake! With these small pics it's hard to tell though, especially if you're a MAC newbie.