In Ireland a few souts have been found with rock art in them. Ogham stones are more common (see Drumlohan for the most excessive example.)

Sometimes RA is used for lintels or at bends.

There are two maoin ideas behind the re-use of ogham stones.

[ol]Ogham Stones stopped having meaning and were useful buiding blocks.
[*]The were used in the souts to protect them from the Church who may have wanted to destroy them.
[/ol]]

Both arguments could apply to RA. Most Irish souts are later than the Scottish ones (apparently).