It depends on what the company promises its customers about security, privacy, and recoverability. The paper's point is that methods for adding lawful intercept for one party tend to result in intercepts by other parties.

Far as write or collaborate, you should look up the Lavabit case records or summaries. The FBI and court demanded that he hand over the master key compromising all users then lie to them about it. FBI also wanted to put a black box in a privileged position that could probably be used to compromise the service. They've used 0-days before in ops.

So, a backdoor with enough privilege to read everything in the system, install updates with their spyware, and be unnoticeable to OS must be both (a) enormous technical risk and (b) have write access that could enable corrupt officials to frame dissidents. I've worked on potential counters to A but B is unacceptable given fed's and spook's track records.

Yes, that's what happens when the government and the company don't work out any compromise. In the end, if you stonewall and the judge agrees, the government gets to use coercion and shut you down. There are worse things (they could raid your datacenter or fine you or put you in jail).

In the happier case (with better lawyers), a legal procedure gets worked out where the company checks that the search warrants are valid, law enforcement gets the info they want, the company keeps their private key, the government doesn't get to install any hardware, and companies publish "transparency reports" showing that mass surveillance isn't happening.

Those are the ones you hear about. Then tgere's the ECI level Snowden leaks on US companies "SIGINT enabling" their products. It said the FBI "compelled" those that resisted. SIGINT enabling is backdoors. The method of compelling isnt revealed. And Lavabit case was similarly expected ti keep secret of it all.

So, you are told that it happens as you describe. We cant be assured of tgat given leaks.