Multiple torrents on a single file.

Say that there's a tv-show in three parts: A, B and C.

And I've got two torrents. One with the parts A and B. And one with the parts B and C.

Can I let the two torrents write and read to the same file, given that I let the torrents save to the same directory and that I use the same client (µTorrent in my case)?

Not at the same time since each program optains a lock on the files while it has them opened. The other program would simply get its access denied from the operating system when it tries to open them.

But you could just let one program download the files in B (preferrably the one that has the torrent with more peers) and tell the other to only download the other part (A respectively C).

No need to use multiple clients.  Just use one client and deselect the common files in one of the torrents.

I doubt you can download B from both torrents simultaneously.  But I'm pretty sure you can *seed* the completed B for both torrents.  Just make sure both torrents can see that B is complete (i.e. use "force recheck" to be sure).