That's a good question. I've heard this question answered both ways, "yea" Amtrak "could" possibly use it, and "no" it is being built purely to "HSR" standards, in public. And since they never seem to be able to give the same answer twice in a row, as with so many unanswered CHSRA questions, who really knows?

Many other systems are "interoperable" with existing technology like in Germany, France, Spain, though HSR more commonly shares existing "conventional" tracks to allow access to urban centers, or branching off of the HSR segments to allow access of HSR to stations on connecting "conventional" routes.