Over on the Warhammer Community site is an interesting article comparing the new Legions Imperialis miniatures with Epic miniatures of old.
The new Legions Imperialis models are much bigger than the Epic versions. This probably means that it will be challenging to use any Epic models alongside the new ones. Many of the models were pretty much underscale anyway.
One mistake in the article is that they mention plastic Leman Russ tanks
On the left is an adorable family photo, depicting three generations of the Leman Russ. At the front in green is an old metal version from the Space Marine-era in the mid 90s, joined by a plastic model (we think) from Epic Armageddon. The new Legions Imperialis Leman Russ kit also builds Leman Russ Vanquishers, pictured on the right with a smaller plastic version below it.
These plastic models were in fact resin models from Forge World. Here they are advertised in the Forge World catalogue.
I had a few, but as they didn’t match the metal Epic 40000 models I had, so I sold them on eBay.