"He says that he can build a mile of tunnel," LeFrak said. "He's obviously a force of nature," he added. "This guy is an imaginative guy."
Earlier this month, Musk tweeted a symbol of his tunnel idea, dubbed "The Boring Company."
"The real problem with doing this is gaining rights of way, gaining eminent domain, or having the rights of way to get the real estate to build the tunnel," LeFrak said.
"[Musk] still has to prove the concept," he argued. "But at least here's a man ... doing something a little unusual, thinking out of the box, and willing to invest his own capital."
On Thursday, another one of Musk's visions, a super-fast hyperloop transport system, appeared to take a step closer to reality with the release of test track photos.
The hyperloop is seen as a way to cut long-distance travel times as well as a way to help reduce congestion in many cities.
Musk attended Trump's infrastructure meeting on Wednesday at the White House, along with other business leaders including LeFrak and his infrastructure council co-chair, fellow New York-based property developer and Vornado Realty Trust chief Steven Roth.