It certainly sounds like a scam. Looked around a bit online and see a LOT of complaints from people who say this company posted a similar notice on their home for no apparent reason. It also seems like they are using a generic name that sounds similar to other legit companies. I also have no idea what the term 'preservation services' means, sounds like part of the scam to be as vague as possible.
No one has any legal authority to do what they claim they are doing. They can't just swoop in on some apparently vacant property and claim it as their own, title to a property doesn't work that way. If the property has a mortgage, the bank is only one with legal rights to it. Claiming they can come on your property and change the locks (not even sure how you would do that without breaking into the house if doors are locked) is illegal. Seems they also run a similar scam when a house is being remodeled so perhaps they can more easily gain access. What their endgame is not clear to me but certainly sounds like a scam.
Only if a house was in foreclosure (for example) could the bank/mortgage company engage with a 3rd party in some sort of activity to repossess the property. This doesn't seem to have anything to do with that. I would certainly call the local police since likely this scam is taking place in that area with other homes impacted as well. I would not call the number on their notice since part of the scam is an effort to get other personal information from you as part of some effort at identify theft. Whoever answers the phone is clearly in on this scam and will cite some bogus legal mumbo/jumbo to justify their actions.