Biofilm is a self-assembling microbial community that can serve as a model system for studying emergent collective dynamics of living systems. Bacillus subtilis biofilms resolve a conflict between interior and peripheral cells by electrical signaling and oscillatory colony-growth dynamics. Intriguingly, this dynamics maintain the interior-cell populations within a biofilm, which ultimately improves the survivability against antibacterial treatments as a whole. Beyond intra-biofilm coordination, two biofilms in a microfluidic device can coordinate their oscillatory phases according to the nutrient availability, through which biofilms improve their survivability by effectively utilizing limited resources. While models that can separately simulate intra- and inter- biofilm oscillatory dynamics have been proposed, recapturing these dynamics by a simple phenomenological model remains to be done. Extending from our previous work where we developed a simple reaction-diffusion model that captures the essence of the oscillatory colony growth dynamics of a single biofilm, here we show that a model similar to our previous one can recapitulate the inter- as well as intra-biofilm dynamics.