My former boss invited several different entry-level attorneys for in-person interviews, based on their undergrad. His reasoning was that they were still young enough in the legal industry, so it made sense to review both their law school and their undergraduate performance.
Further, he specifically second-interviewed a guy who went to an HYP undergrad and a second tier law school. He thought the candidate was excellent and wanted an opportunity to determine why the discrepancy in rank between UG and law school. Turns out that the candidate's reason wasn't compelling, but it does provide anecdotal evidence that employers look at more than just the latest academic entry on a resume.
My current boss has strong ties to her undergrad, so it absolutely plays a role in our hiring.
I didn't go to an Ivy undergrad, but I attended an Ivy law school. When I lateraled ~ a year ago, there was a small but vocal minority of firms who wanted to talk about my undergrad. Again, anecdotal evidence, but I'd say the undergrad does matter somewhat....just another soft factor to throw into the mix.