No, they normally just disable it, or it might just carry on running until it next needs an engineer reset, at which point you're stuffed. They won't give you engineering access to it though. They would only come and remove the panel if it was quite new, or if there is a contract term saying they can charge you for removing it if you cancel the contract. None of the other bits will be worth removing unless they can charge you for doing so.
If you do buy it from them, make sure you get the installation manuals and engineering access code. Often they won't give this to you even if you do buy it, so you basically wasted your money.
Generally, you find that you don't own an alarm unless you know the engineering access code.