How to synchronize "Other" subscription based read only calendars i.e. "Contact's birthdays and events"

[Guest iwciakk]

If one fill in birthday data to their contacts in Gmail one can subscribe View only calendar called "Contact's birthdays and events"

As well there are other usefull calendars one can subscribe like Holidays for particular country.

My question is how to synchronize this subscription based calendars ?! :D

They do not show up on my Android phone so I can not choose them to include them in sync process.

TIA