There isn't enough time for Phil to be briefed on everything the teams do during the leg, but he gets a lot to work with from production on site at the check-in mat. Hence, his questions to teams on the mat. He was obviously told about the alliance beforehand since he asked about it when the first three teams arrived.
The Cowboys are staying out of the line of fire of the other four teams, which is smart since it means they aren't the targets of the other teams. They're most likely couldn't figure out Brenchel's U-Turn strategy in the last leg, either, and they had no reason not to be cooperative about staying ahead of them once they got to the William Tell statute.
(I've already calculated the placement averages and trends, but I probably won't get them up until sometime Monday. More bad weather is coming in tonight, and I think I'll have less worry about connections tomorrow than I had earlier today.)