The overwhelming reason why companies undertake investment is to exploit market opportunities for the goods and services that the investment supports. Cutting the rate of company tax can lead to a marginal increase in the after-tax rate of return of an investment - but only if the project is profitable in the first place, and that depends on demand and broader economic growth.
Because of dividend imputation in Australia, the role of company tax in influencing investment decision is even more marginal than in other countries - it is mostly only foreign shareholders that would benefit from a cut in Australia's company tax rate.