Complex sentence: Because of the high cost of converting existing rail-based lines, this is no longer done in Paris, nor elsewhere; now rubber-tyred metros are used in new systems or lines only, including the new Paris Métro Line 14.
Split into simpler sentences: Because of the high cost of converting existing rail-based lines, this is no longer done in Paris, or elsewhere. Now, rubber-tyred metros are used in new systems or lines only, including the new Paris Métro Line 14.