Can and should old heat recovery line (15 years old) be reconnected with new Trane 14 seers with R410A?

How you can confirm that your contractor is really using R410 with Trane?

All A/C condensing units have the refrigerant used listed on the information tag on the unit, this tag will be on the outside of the unit. All componets installed in 410-A systems have to be certified for use with 410-A, because it works at a much higher pressure then R-22.
My own personal opinion on reconnecting the recovery unit is no, it is fifteen years old ,this unit may not be constructed to accommodate the recovery unit.(Check with installing contractor)