Here's Bookmaker's policy on baseball. I'd say it's pretty standard:
Official Game Time
Winners and Losers are official after 5 innings of play unless the home team is leading after 4½ innings. If a game is called or suspended, the score after the last full inning determines the winner. If the home team scores to tie - or takes the lead in the bottom half of the inning and the inning is not completed, the score at the time the game is called determines the winner. Monies will be refunded if the home team ties the game and it is then suspended. Events will not carry over to the following day (unless otherwise specified). BookMaker does not recognize suspended games, protests, overturned decisions, etc. for betting purposes.
When betting on the total runs (over/under) the game must go 9 innings (8½ if the home team is ahead) to have action. Wagers on total runs will be refunded if a pitcher change occurs prior to both listed pitchers throwing at least one pitch. Rules for the run line wagers are the same as those for baseball totals.
Game must be played on scheduled date and site.