Can phone (land) lines get crossed in one household (two seperate lines and two different telephone companies)

I rent an upstairs apartment, and, so, thus share a house with my landlord. We both have separate landlines with two different telephone companies. There are times when he is using his phone and when I go to use mine, there is no dial tone. Then an hour later, there’s a dial tone. It’s not a common occurrence (he uses his cell phone, mainly, and is hardly ever home). We have WIFI here, so, I don’t know if that has anything to do with it (technotard).