From what we can understand, the car chase is by the lake. It happens first, possibly in the PTS.
This sequence in Siena happens latter, probably after White is interrogated in the underground safe house.
But the Siena stuff could be two separate sequences, we know that the art gallery fight is in Siena too.
So that would be:-
Underground in the bottini,
On the ground: Piazza del Campo and nearby streets,
Above the ground: on the rooftops
and
In the Gallery (up in the tower, through the dome and into the big hall on the scaffolding and ropes.)
But with the chase that involves the Bottini ending by the fountain during the horse race, I am starting to see this as two sequences, (three action sequences in Italy in the first 20mins does seem like a lot)
Here's how I can see it playing out:
- Bond is preparing to bring Mr. White in for questioning (and is somewhat apathetic to his leg injury)
- Unfortunately, the party gets crashed by the arrival or Mr. Slate and Elvis, who have come to kill White because the Organisation suspect Vesper sold him down the river
- The car chase involves Bond and White in the Aston, trying to get to the SIena safhouse while being hounded by Slate and Elvis
- Halfay through, Bond realises their arrival was a little
too convenient, and realises they were after another target: Rene Mathis, currently being questioned by M in the Siena cisterns
- Bond attempts to lose them, resulting in the explosion
- Cue titles
- When we return, Bond has given Slate and Elvis the slip and is now bringing White into the safehouse
- White and Slate are cunning bastards, however, and managed to follow Bond and White to their other target: Mathis
- Bond leaves White with M and the MI6 staff, and starts chasing them through Siena
- Bond and Slate end up coming out of the
bottini and Slate is trampled to death.
- Alternatively, Bond kills Slate in the art gallery and chases Elvis out of the
bottini; Elvis escapes in the middle of the crowds and confusion.
Essentially, it's an extended chase with a slight interlude in the middle; you think the chase is over once we get to Siena, but it's only halfway through.