AVery pretty. I would like to know that technique as well.
ACheck out the craftsy.com class modem piping
That looks like a stencil with royal icing to me...
I think that this scroll work was piped freehand. If you take a closer look at the pattern detail on each tier, its looks similar rather than identical - as would be the case if a stencil were used. My guess is that the piping was applied after the cake was stacked.
One way to approach this technique - is to use some tracing paper and a pencil. Draw an outline of the scroll work freehand or from an existing pattern, and then transfer to cake using a cake scriber or sharpe needle,
Using a plain No 1 tip and royal icing, pipe the outline, allow to dry and pipe over this again, gradually building it up - for a more defined scroll design. Apply more pressure at the tip of the scrolls. When piping the dots detail - use more or less pressure for size variation throughout the pattern detail
One final suggestion, if you could source a stencil with scrolls. Position stencil directly on cake and apply, using royal icing. Allow to dry and pipe over outline.
P.S Try Google for a scroll pattern - or another good source for inspiration would be from some wallpaper designs.
Hope this helps!