If you notice, the CB runs down the rail until it gets to the side pocket, then deflects of the nose of the pocket and diverts off the rail line. There is a trought (mentioned above) on all but new cloth at the side pocket.
The correct way to play this is to use a bit of low and a bit of right on CB and aim a couple of mm outside the side pocket and have the CB massé back onto the rail after the side pocket. This shot works even when the rails are not "dead straight".
Good answer here. You want to use a bit of inside english to hold the cue ball to the rail. The points of the side pocket must be perfectly aligned or you will hit the far point going down the rail. It takes a good table mechanic to set up a table so this does not happen. One trick I learned from Danny D. was that just before hitting this shot he would pull in the far point of the side pocket with his hand (perfectly legal). It takes a few seconds for the point to return completely to its original position. Enough time to shoot the ball past it. Try it, you'll like it.