Most likely the mirrors are hung with wall anchors through small holes in the mirrors behind them.

or they may be...

Kerrie Kelly one of the Houzz professionals stated: "It looks like they may be framed like artwork and then cleated on the back. That way the cleat can go into the tile and the opposing cleat can click in from the mirror back."

-Most likely they are not adhered to the mirror.

The tile isn't adhered to the mirror - Those are two separate mirrors that are hung over the main large mirror.

Kerrie Kelly had stated this on another photo:

https://www.houzz.com/discussions/how-were-the-mirrors-installed-over-tile-dsvw-vd~25272

and it looks like a similar application to me.

Any mirror installer could answer that for you

The plate mirror was adhered on the wall. 2 separate mirrors with Capiz shell frames, were then anchored to the wall through holes in the plate mirror.