This mainly has to do with the ISO 9001:2000/2008 certification, which is a formalized quality management system to help businesses meet the needs of both customers and other stakeholders in the company. Proper quality management that is extensively recorded (phone, computer, and manual transactions and communications) and tracked improves business, and has a positive effect on investment, market share, sales growth, sales margins, competitive advantage, and avoidance of litigation in many cases. Whether you are a customer or a contractor who calls in, the call will be recorded, any notes taken will be saved, and everything will be coded into a searchable and trackable database so that things like problem resolution can be tracked and graded. When you are on HOLD, it's still part of the process, and definitely part of the phone call, and the recording can stop or continue solely at the discretion of the party recoding the call.
Most businesses announce the possibility of the phone call being recorded or monitored because the ISO 9001 certification says they have to do so. The ISO standards are worldwide standards, not dependent on local laws. If you want that ISO certification, you have to do the things which are required to get and keep the certification.