I've actually been trying to embed from Piapro recently, too. It's only indirect evidence, but it looks like it's possible from this post on vocadb:
We specialize in Vocaloid and UTAU content, both Japanese and overseas, so the site includes multiple features designed with that in mind. For that reason, the site supports embedding media, such as PVs from Niconico, YouTube and piapro (among other sites), that are popular among the community. Users can choose to view titles in the original language or see translated names instead.