(Image 1)When a redstone line goes up a block, the two pieces connect in a line and power is passed.

(Image 2)When a solid block interrupts the line, the two pieces stay as a cross and power stays on one piece only.

(Image 3) If a piston blocks the line, the bottom piece of redstone appears as a cross, disconnected from the top one yet it still receives power from it. I think this is a bug.

What should probably happen: the cross is disconnected and is not powered OR the line is connected and receives power.