The question of legal responsibility has no clear answer.
Laws are changing and every situation is different.
Landlords and property owners do have legal obligations to provide safe and habitable accommodations for tenants. Bed bugs may be considered an unacceptable condition.
Tenants have an obligation to cooperate with owners and landlords. This includes preparing the unit so the pest management professional can easily inspect rooms and treat if necessary.
You are legally liable if you misapply an insecticide or apply it without a license. In most cases, landlords, owners, and building managers cannot legally apply insecticides unless they are licensed to do so.
The best recommendations are to fully communicate with all who are potentially involved, inspect regularly, take immediate steps to remediate a bed bug problem using a professional pest control company, and document everything.