As said without correct equipment you wouldn't know standard from remapped, afaik BMW, certain Indys and tuners will/can
upgrade the ECU with the latest factory map for your car. (Is that correct Enda?)
Yea, anyone with autologic should be able to force an update and write over whatever is in there, same as BMW, but they wouldn't know if there were changes.
Kit like that looks at the part number for the software, and it'll have a list of updates if they are available. The part number of the software isn't touched in remapping, and the ECUs any corruption monitoring will also report that everything is as it should be.
What BMW or others would do in a case like this is either apply an update, or reporgram the current version back on so they can be sure it's original, but they wouldn't be able to tell if they have written over anything.