Looking at the schedule that Mario posted, WBZ carried the NBC Saturday morning lineup in-tact, except bumping Saved by the Bell to 1pm instead of keeping it at its 11am (ET) slot with the rest of the network. From other Boston-area schedules I've read over time during or around this timeframe (mid-80s to 90s), it seemed like channels 27 and 68 usually would carry whatever network shows the Big Three (Chs. 4, 5, and 7) didn't clear.
The 1990-91 TV season was to the second-to-last season that NBC aired animated shows on Saturday mornings until 2002, when Discovery Kids on NBC started up. Saturday Today launched in fall 1992, and the TNBC lineup followed it in most markets, although in some markets, local news aired in-between.