Here's info on ISDN BRI service from a page at Verizon: I don't know
if it's left over from an earlier era, or if Verizon is still selling
ISDN BRI lines to government customers in any of the areas where it
operates.

I'm taking a trip down memory lane today, and tomorrow I'll
concentrate on all the latest Fiber-to-the-soup-bowl,
satellite-delivered-nonstop-porn, and Voice-over-Intermittent-
Provisioning services that are supposed to give us all attacks
of The Vapors these days.

>From the Verizon site:

Benefits

* Help Increase Productivity. Using ISDN BRI's higher speeds - ISDN
BRI utilizes two separate 64 Kbps channels that can be combined
into one 128 Kbps channel.

* Faster Data Transmission Speeds. Result in quick connection times
and low usage costs.

* Avoid Costs and Inflexibility of Dedicated Lines. The same ISDN
line can be used to carry both voice and data, so there is no
need to wait for a fax to finish before making a call.

* Productivity-Enhancing Applications. Take advantage of these
applications, such as remote Local Area Network (LAN) access,
videoconferencing, pre-press graphics, postproduction editing and
digital broadcasting that can reduce travel costs and product
development time.

* Clear, Digital Transmission. This results in few errors or
re-transmissions and provides a highly reliable network - all of
which can help increase productivity.

* Back Up Overflow-Dedicated Services. ISDN can be used to protect
against outages or to provide cost effective insurance against
high-volume congestion for mission critical information. In a
large government office, ISDN may be provisioned for use as a
disaster recovery backup.
https://www.verizon.com/business/solutions/public-sector/federal-government/contracts/wits3/products/integrated-services-digital-network-bri/

--
(Please remove QRM from my email address to write to me directly)