Expansion joints/Seismic joints

[Fatalxception]

Is everybody else allowing enough of a gap in roof thermal expansion joints (example in single story metal deck) to satisfy the seismic joint code requirement as well. I don't usually see this done. Since the buildings are acting separately perpendicular to the joint, I think a seismic joint would be required.
Also, is a seismic joint required when 2 buildings that have the same period are next to each other. For example, I am separating 2 buildings by a firewall. Each building butting up against the wall and not connected. If each building is moving at the same period, can they still theoretically smash together in an earthquake?