They're not from the Beecher's triliobite beds. They're from a different locality that bears "bugs" "relatively similar" to those from the classic Beecher's site. The new locality is in the Whestone Gulf Formation; the original Beecher's Trilobite Bed is in the Frankfort Formation.

I just perused the scientific paper published in Geology. Quasi-interesting, but not spectacularly so. The egg-bearing trilobite merely confirms already well-established, long-held hypotheses that trilobites were brooders, carring their precious egg cargo in special "recepticles"--located either externally, or internally in the cephalon region.

But anyhow: A quote from the paper regarding the locality information:

They're "from the Martin Quarry in the Whetstone Gulf Formation, Lorraine Group (Fig. 1; see Farrell et al., 2009, for stratigraphic description). The Whetstone Gulf Formation is a set of dark mudstones and siltstones that represent distal turbiditic sedimentation in a deep-water, low-oxygen environment (Farrell et al., 2011). The paleoenvironmental conditions at the Martin Quarry are relatively similar to those at Beecher’s Trilobite Bed"