csdude55, I can't answer your Facebook question, though my guess is that the answer is probably not. The introduction to your question caught my attention, though, and does raise a bunch of flags, and may have bearing on the FB issue.
You had posted...
My company has about 60 websites, and I was recently able to purchase a decent domain to umbrella all of them; let's call it abcd.net.
Not to take this off topic of Facebook... I feel compelled to note that you are very likely to have an issue on Google with the "60 websites" all funnelled into one domain.
Many years back, I was confronted with the question of redirecting maybe a half-dozen domains into one, and did some research and discovered that Google does watch these things. I had it on good authority that too many redirects to one domain, at that time, would result in a spam penalty. The precise number was considered part of Google's "secret sauce" and wasn't mentioned, but a figure of about 30 did come up.
It was also made clear that the issue wasn't about redirecting multiple alias domains into one... as some large companies have many more than thirty.... It was about redirecting too many
previously promoted domains into one, as if "link juice" containing keyword rich anchor text and PageRank (the model at that time) flowing into one domain might skew legitimate rankings. My guess is that sixty websites that had been on the web for a while would likely be considered previously promoted.
The Google algo is way different now from what it was 15 years or so back, so I'm not sure what would apply now... whether it's even a concern. My guess is that with 60 sites, there probably would be an issue... and these might resemble doorway or satellite sites.
(Another Google digression... if you're going to merge very many sites, do it very slowly, just to allow Google time to sort things out.)
Getting back to your Facebook questions....
Google and Facebook "algos" are way different, and I don't know whether FB has a popularity measurement analogous to PageRank... call it "Like juice"... but, if they did, FB would probably be suspicious of merging 60 business Pages. You might do a reality check on the numbers, to see how many real likes each of your client's Pages has.
My guess with Facebook, btw, is that it simply doesn't have the tools to do what you want to do... but I leave that to others to answer.