Unfortunately no. Although many servos are close, some very close, they're not all exactly the same. I don't know about the two specific servos you mentioned, but more than likely, to change servos and brands entails some mods for the mount. It's best to build for the servos you want, mount them then leave them for the life of the plane. If you later need to replace one, to exactly match the holes and sizing, the best way to guarantee the fit is to replace it with an identical servo. If necessary you can fill the servo screw holes with epoxy, then redrill for the new servo, if it fits in the servo cutout or rails.
For Hitec and Futaba, if you go to
www.servocity.com , they have diagrams showing dimensions and hole spacing, etc. At least that gives you info for those servos ahead of time. I have to assume somewhere, similar info is available for JR servos, then you can know for sure. Someone will probably post the JR info for you to look at.
Edit for URL fix