He hangs up as soon as Jack starts singing, really not in the mood for it. When he does arrive in Sector Zero he'll find Ianto pacing around, exploring his surroundings and looking for answers. He won't move to embrace Jack when he sees him because that's not the dynamic of their relationship yet. It's more than just sex but it's not serious enough for public displays of affection.
"Please tell me you have some sort of dramatic plan to get us out of here." He always does after all.