When using the Masuda method you have a 1/1024 of finding a shiny.
Pokemon found in the Friend Safari have higher chance of being shiny however it hasnt been confirmed how higher (higher than normal wild encounters, not the Masuda Method :P).
The exact rates at which the previous five techniques increase the Shiny probability have not yet been conclusively determined.
So to answer your question, we dont know yet, although based on fan experiments it is believed to be a 1/600 or so chance, which is more than the Masuda Method.
Source and source.