There simply is no Palestinian-Israeli agreement on Jerusalem, right of return, settlements etc That's why the Palestinians turn to the Quartet to get them what they want. The Quartet would give them the 1967 borders but not the right of return but the Palestinians want both. Israel will give them neither.
10 arrested at Israeli Arab protest in Ramle (Haaretz)
from the article: Peres: Israel needs to formulate its own Mideast peace plan