The taxi (approaching from the left) obviously saw the fire-engine coming and stopped. Traffic coming in the opposite direction (to the taxi) was shrouded by the building.
First watch the video here:-
http://news.bbc.co.uk/1/hi/england/8251504.stm
then watch the video here (00.05 to 00.08):-
http://news.bbc.co.uk/1/hi/england/b...ts/8250244.stm
to appreciate the 'terrain'.
I know the junction well, having lived in Luton and worked there for many years.
The fire-engine was 'moving' . . .