Question about a standby director

[Jack Bauer]

I was looking around IMDb and stumbled across the A Prairie Home Companion trivia page and saw this:

For insurance purposes, and in the event that 80-year-old director Robert Altman was unable to finish shooting the film, Paul Thomas Anderson was employed as a standby director.

Now here's my question: Does a standby director finish the film as the director intended or does the standby director finish the film as his or her own film and ignoring the director's intention for said film?

 

[SolidSnakeMGS]

Well, its probably harder for a replacement director to finish the film as intended by the original director, depending on how far along the film is, not to mention directing in a style different from your own. I imagine its a combination of the two, where the new director implements what he percieves as the original director's vision while still directing as naturally as he can.