So are you looking at buying this place? If so, then as part of your normal surveys just get a competent electrician to conduct an inspection and go from there.
And no, MICC would not provide a 'giant earth rod' as whilst it would maybe introduce some additional parallel paths to earth (and only where it's not been installed correctly!) that doesn't count towards the earthing system of a property because the measurements that are taken to determine that are those of the supply end, with parallel paths disconnected. Additionally, you won't find any reference to it in BS7430 as an approved method (even if it did work!)