I read somewhere that Lucasfilm and Sierra had a meeting of some kind in the early days of Scumm, and that Lucas' crew was duly respectful because Sierra was their role model. Can't remember where that was, though. So there's nothing to be seen here. Please move on.
(But maybe Jane Jensen has some dirty secrets to tell. 
)
EDIT:
A 2 hours talk by David Fox about Lucasfilm Games in which he mentions Sierra a few times and even Amiga.
http://scene.org/search.php?search=david+fox&x=0&y=0
Also on Youtube in lower quality.
http://www.youtube.com/view_play_lis...84A72CC67AB196
(Sorry for being OT, but as long as there are no news on Mr. Avellone...)