WOW that's nice !! Haha this reminded me of my visit at Ajisen Restaurant at IMM a few months ago. I went there to have my dinner with my friends and I remembered they were playing the whole Koda Kumi's BEST~second session~ album (not full blast though lols)
I have also heard Ayu's songs being played at Daiso and Namie Amuro's songs being played at Yoshinoya before too

I will feel happy whenever I hear J-Pop songs being played in the public...hearing them would just made my day