According to the new Necron codex, there were in fact some Tomb worlds awaken during the crusade:
| The awakening has been far from precise, and the Necrons have not arisen as one but in fitful starts over scattered millenia, like some gesalt sleeper rising from a troubled dream. Errors in circuitry and protocols ensured that a revivfication destined to take place in the early years of M41 actually began far earlier in a few cases, or has yet to occur at all others.The very first Tomb Worlds revived to see the Great Crusade sweep across the galaxy.|
Not only this, but Trazyn the Infinite is stated as having woken far longer before other lords.
So does this mean that Necrons can now be used for forces, other than Androids now?
Yep! Sure does.
im gonna get cracking on a necron army that awoken in either the great crusade or horus heresy.
Not only has Trazyn been awake longer than most Necrons, but in the WD released just after the necrons, in with the battle report, there is a portion of fluff where Trazyn speaks of a history between him and Roboute Guilliman so there is a huge connection to the Great Crusade to explore.