substantial shareholder

I have come across something interesting...
On friday Mcaleese Transport popped up on the substantial shareholder registry of Boom Logistics. This company is heavily involved in the crane hire industry with significant operations in the Bowen Basin (coincidently where Boom has significant operations as well). They have prudently been buying Boom stock since March and now own 6.4% of the comp after spending just under $9m. Pretty strange for an unlisted company such as this to allocate this sort of money...taking a stake in a listed competitor.
there has been scuttlebutt for some time that further consolidation in this industry was inevitable.