You can open the .poke files located in */Pokemon/maps/poke/Route30.poke ... that is a list of all available Pokemon for that Route. The second Number says what Pokemon will appear.The third is the probability for that Pokemon. The last few numbers indicate the times when the Pokemon is available. If there is 0|1,2,3,4) the Pokemon is available in the night and in any season. 1 may be Spring and so on but I'm not sure about that.