Quick update: Bolivia

I had recently written about the political stand-off in Bolivia. Now the BBC reports that three opposition senators broke ranks and voted with the government on President Morales' land reform bill. Democracy, though very fragile, is hanging on.

Update to the update: the anonymous commenter alerted me to the fact, not reported by the BBC, that only one senator voted. From CNN:

But Tuesday night, one Podemos senator returned to the chamber to vote for the land reform, joined by assistants filling in for two other opposition senators.

It was not immediately clear whether the assistants' votes would hold up to legal scrutiny.

Now, who exactly were these assistants? What legal right do they have to vote?