In the pub poker league where I deal, this is one of those situations where we bend the rules in favor of keeping it simple and friendly.
When a player is waiting to sit, and the BB gets knocked out, the new player takes his seat. But because normally the next hand would be only have one big blind, the new player has the option of being the sole BB, or waiting two hands. More often than not, the player chooses to get in the game immediately.
However, when breaking a table, if one of the remaining tables would have a one BB situation, we will put the SB from the broken table into the SB seat and allow him to play. BB gets the UTG seat. Button goes behind the button, etc. We only do a blind random seat assignment when merging to the final table. Again, just to keep things as quick and simple as possible.
Frankly, I can see both sides of the argument for what a poker room should do.