Thanks for sharing the interview. I was struck by this Lou quote:

"Well, surprisingly enough, I tried to put myself in that same voice, and with a little a little work I was able to duplicate it to the point where you wouldn’t know if it was sung 30 years ago or if it was now."

I hear his current older voice on Long Gone, True Blue Love Unplugged, and Deeper Side of Love. I wouldn't say it's seamless (it's actually fairly obvious), but he sounds good. Same with the Foreigner tracks he added vocals for recently.