Is there a way to use a Subpod if our available garden bed space is only about as wide as the pod itself? We would have available extra garden bed space on the left and right (shorter) sides of the pod, but not at the back and front (longer) sides.

Is there a way to use a Subpod if our available garden bed space is only about as wide as the pod itself? We would have available extra garden bed space on the left and right (shorter) sides of the pod, but not at the back and front (longer) sides.

You could fit the Subpod into your narrow garden bed if the interior garden bed space is just 1-2 mm over 45 cm wide at it's narrowest point. 
The worms would still be able to move in and out from either side of the Subpod.  It's not ideal though, because the soil surrounding the Subpod helps to keep the temperature inside the Subpod more uniform when the outside temperatures change.   
The risk here would be if your garden bed was located where either the front or back walls heat up excessively with summer sun.  That heat could be transferred to the interior of the Subpod and possibly affect the worms.  Otherwise, it should function well.  If there was a lot of sun hitting the walls near the Subpod, you could potentially install shade clothes or similar to stop the excessive sun hitting the surrounding walls, e.g.