I don't believe it is so easy in avast 5.0 as the update process involves many different files, unlike in 4.8 where it was one file the 400.vps file.
I don't know, all I do know is that there is no longer a 400.vps file which used to contain the complete signatures.
Now there are folders relating to vps version numbers at about 45-50 MB each there might be the current version and the previous one as both could be in use. there is also aswdefs.ini which records which the latest version is, but I believe there are other connections, registry, etc. which also play a part.
The short answer as an avast user like yourself, I simply don't know the full technical workings of the new avast5 update process.