The "historical utility nature" of wireline carriers was due more to technical limitations than to regulations: cellular exchanges were built after reliable network-based data transfer methods were available, so cell carriers were never burdened with the electro- mechanical infrastructure that the baby Bells were using until well into the 1990's.
In decades past, there was a *big* differnce between some "landline" and cellular call data, caused by the need to transfer Call Detail Records created at older electro-mechanical central offices to centralized billing systems before it could be tallied. Since the data was either punched into paper tapes, or recorded on IBM-type reel-to-reel magnetic tapes, there was a large time delay before it could be made available to law enforcement officers. There was also, of course, reason to limit the /amount/ of data recorded, since too much data would have overloaded the AMA (Automatic Message Accounting) systems, and that's one of the reasons why "Unlimited" local calling was offered in the first place.
Now, almost all traffic is supervised using a packet data switching network called SS7 (Signalling System #7), and that means that any government agency which wants to gather "pen" data only needs to sip the call-control traffic which is transitting the SS7 Signal Transfer Points (STPs), and sample the calling/called numbers from within the packets.
However, not all cellular metadata is handled through SS7, and the stuff that isn't has more information in it, i.e., the identity of the cell site which is handling the call at any moment. That means that the cellular call data tells an investigator more-or-less *where* the cellular phone was during the call.
The LUDs are Local Usage Details, and they are the call records of specific phone numbers. Depending on the company which generates them, and what state(s) the calls are completed from and to, the LUDs might be gathered at a locel (Class 5) central office, or via traffic monitoriing systems such as Hewlett-Packard's AcceSS7 (which sips SS7 data at the STP sites), or at a tandem office owned by an Inter-LATA carrier, or via the cellular carriers' proprietary systems.
Long story short: "pen" (i.e., call usage) data has been available to government watchers for a very long time. The only thing which has changed is how long it takes a cop to get hold of it after a call is completed.
Bill