No. Every i9300 has a unique IMEI and calibration. Cloning EFS files is (violates telecommunications laws in most countries) and will cause network conflicts if both phones are active.
The is more than just a set of encrypted bits—it is the digital soul of your Galaxy S3. It holds the identity that connects your phone to the world’s cellular networks. Losing it is a rite of passage for many Android modders, but also a source of endless frustration. i9300 efs file
(low success rate)