In multiple European cities now I see taxis being allowed to use the bus lane (while of course regular cars are not).

What's the policy justification for this?

This is used to encourage the use of public transportation instead of personal vehicles to prevent excessive traffic congestion.

but they can transfer multiple passengers to different destinations, and on the other hand, encouraging people not to use personal vehicles can ultimately lead to increased use of the metro and buses.
i'm not a fan of this move, but my guess about their goal is this.

But for the purposes of congestion management, taxis *are* personal vehicles?