Hoosier,
Seems like wherever you're at, they move players the old fashioned way. That was the old procedure many eons ago.
First off, it's an unfair procedure to do it that way. Why? Any player being moved position for position will lose one free hand before taking the big blind again.
Example: Table 1 is 9 handed, Table 5 is 8 handed and loses the player on the Button. Table 5 is now 7 handed. The player on Table 1 that is on the button is moved. He was due to receive 6 more free hands before taking the blind again (he's already played on hand on the button). Now being moved to an 8 handed table he will only receive 5 free hands. That's unfair.
Also, if you move position for position, now the floor person has to count how many spots off the button that seat is or count spots from the big blind. Lots of floor people can't count. They make mistakes. They miscount.
It's easier for staff and for all players to understand that the big blind is getting moved rather than some random position from the table. Moving players this way does two things: 1) The big blind is always moved to the worst position possible at the short handed table. Meaning they will either take the big blind immediately at the next table or they will be moved into the seat that is closest to taking a big blind in as few hands as possible. 2) Players don't lose free hands, they can only gain free hands.
Now to answer your specific questions:
If the table has lost only one player . Does the moving player just take the open seat where ever it is ?(except small blind). Do they move to the worst position only if there are multiple open seats ?
A table must have a two player difference before another player can be moved to balance (equal) the number of players per table. Players that are moved to balance tables will take the worst possible position at the table that is closest to taking the big blind, including the big blind seat (never the small blind position, even though that is technically the worst position). Note that it is only necessary to balance tables within 1 player (meaning 2 player difference), when the tournament is nearing the money. For fields larger than 100 players, balancing begins at 54 players (6 nine handed tables). Prior to this stage of the tournament tables are only balanced within 2. For more detailed info see
http://www.pokertps.com/rope_7.php