You can migrate your landline number to a cellphone plan in Europe. There is no way to know whats on the other side when you are making a call.
You can't even keep your landline when you move house.
As to the landline number, you can keep your landline number if you don't move into an area where the phone numbers 'region' code is not applicable.
Just like I am sure that is the case for every other country in the world (or thereabouts).
I am curious to know with regard to USA phone numbers where I cannot tell a mobile from a landline by just looking at the number (e.g, UK Mobile numbers can be identified because they are 07xxx numbers) but US mobile numbers look like landlines and have the same area code.
Can you move to a different state and keep your number even if the area code for that state is completely different?
Edit: keeping my number when I moved also made it really easy to filter out these phone calls. Any number calling me from my old area code that I don't recognize is either a spammer or a wrong number. Any number calling me from my new area code is probably legitimate.
You can if its within the same exchange area.