I'm not sure if that ever happened in the Pittsburgh area, but until not so long ago one could get, along with KDKA-2 (CBS), WTAE-4 (ABC), WIIC/WPXI-11 (NBC, I'm referring to its original callsign here as well) and WPGH-53 (Fox) depending on the system:
WDTV-5 (CBS) Weston, WV
WJAC-6 (NBC) in Johnstown (still available, I think on Channel 192, on the Greensburg Comcast system because of WJAC's occasional coverage of Westmoreland County news and regular coverage of its weather)
WTRF-7 (first NBC, then CBS) in Wheeling
WWCP-8 (Fox) in Johnstown
WSTV/WTOV-9 (first CBS, then NBC) in Steubenville.
WBOY-12 (NBC) in Clarksburg
I'm southeast of Pittsburgh, but northwest of the city one would have often found (and still do) WFMJ-21 (NBC), WKBN-27 (CBS) and WYTV-33 (ABC) out of Youngstown. (I give you Greenville and New Wilmington, PA, as such communities, where cable has both Pittsburgh and Youngstown network affiliates.)
Morgantown, which has been (and I believe still is) part of Pittsburgh's ADI, has Channel 24, a PBS station (I don't recall the callsign) that certainly also is a factor in the Weston-Clarksburg-Fairmont area (which also has a Fox UHF that at one time was a religious station and a low-power UHF repeater of Greensburg's religious WPCB-40 in the Pittsburgh market).
I've noted before how WSTV/WTOV turned up on cable as far east as Philipsburg, PA, just west of State College. That area once had on cable Wilkes-Barre/Scranton and Lancaster/Harrisburg outlets (including WGAL-8, even after WWCP was short-spaced into Johnstown), though again I don't know if any three-of-the-same-network turned up in Happy Valley.