No, Trainz routes are not backward compatible. You cannot save a route in TANE, for example, and load it into TS12. It is not even possible, so I believe, to save a route in TANE SP2 and load it into the original release of TANE. A saved TRS19 route cannot be loaded into TANE. They all use different file formats PLUS some of the features, behaviours and asset properties are quite different. These cannot be replicated in the earlier version of Trainz. Its a bit like saving a complex document in Word 365 and expecting it to load straight into Word 2 without any errors.