probably about a month too late but what the hill (valley).
In the very short alternate timeline from episode 2, biffs brothers mentioned that marty caused biff to crash into A manure truck. So this implies 3 things;
1) there has been debate about whether time travels still occur in the alternate timelines as doc and marty couldnt get together for the time travels in them but according to this brief timeline, they still do happen
2) but wait; they state that biff only crashed into 1 manure truck so does that somehow imply that one of the 2 1955 time travels/manure crashes do not happen in this timeline?
3) off topic kind of but this is the first timeline in which biff figures out it was in fact marty who made him crash in 1955. He may piece it together in 2015 but it's still up i the air.