Hey Cactus-
I used to work at GoDaddy (waaaaaay back in the day) -what JohnLee said was correct about it not being guaranteed and each vendor of the "backorder" competing and winning/losing by milliseconds is correct -no one can guarantee because it comes down to random server pings & who happens to be first.
To hedge your bets, as mentioned above, you can buy multiple backorders w/ multiple companies (and if you lose, you don't get your money back, per se, but you can apply that backorder to another domain name -so keep that in mind while spending). Also, if the domain name is already backordered, a
perspective service provider (usually an accredited registrar) cannot sell a backorder for one domain name to multiple people -it can be used as a way to gauge interest in your particular domain -ie: if you can backorder a domain on major registrar's sites, there may be little to no interest from other parties since they will only sell one for that domain -it's just a mild warm & fuzzy, still no guarantee...
Another option you have is reporting incorrect WhoIs information -part of the terms of usage of owning a domain name is keeping accurate & complete ownership information (I've used this one before to obtain a domain ahead of it's time) -if the ownership information is found to be incorrect/missing, the registrar starts the "repossession" process to turn the domain free again for purchase. The standard redemption period time-frames apply, but more than likely the owner can't be contacted to update/verify the incorrect information and the domain expires early, therefore being dropped on the market for re-purchase early.
Hope that helps a little!
:smxB: