Games Workshop have posted a new article looking at using the Tyranids in Planetstrike.
From their website:
There are few armies more suited to Planetstrike than the Tyranids. The wandering tendrils of the Hive Fleets are drawn to life-sustaining planets, where biomass is most prevalent. The unfortunate souls who inhabit a planet targeted by the Tyranids must witness not only their inevitable doom but a textbook example of a Planetary invasion.
Mycetic Spores rain down from orbit, pregnant with warrior-beasts who disgorge into combat. Lurking creatures break from the shadows to disembowel soldiers and propagate a feeling of terror amongst the frayed minds of the defenders. Even the planet’s own vegetation will turn betrayer as the bio-ships hanging low in orbit saturate the atmosphere with genetic agents that force the native plant life into a growth spurt.