I am not a lawyer nor an LEO.
But I have been around a long time and there are a few things I know.
First, the cops do not have to gain entry to serve a warrant or summons.
All they have to do is encounter the person on whom it is to be served in a situation where they can serve it.
That is usually very easy. The officers of that company are not going to stay in the cave for 10 years.
Also, unless the crime is a serious felony crime involving danger to the accused or others such as murder, suicide, etc., a summons by both registered and certified mail is legal in most jurisdictions.
So I am surprised at the statement that no one has been able to break in to serve a court order, since breaking in is not required.
I'll bet the tunnels lead to dummy datacenters and they route the utilities from there to not draw suspicion.
Two floors of the bunker are living space with luxury amenities and the leader does pretty much live underground. There are numerous warrants for him. He does come out sometimes based on photos but they can't find from where.
He is selling server space at a HUGE markup and making tons of money to be able to pull these shenanigans. They only accept cash and the number of servers is secret so nobody knows exactly how much is made.