Unions have been caught off guard by the June 17-signed FTA arrangements which will remove the mandatory skills assessment requirements for 10 occupations when it comes to importing Chinese workers under the 457 visa scheme.

Three class types of electrician are on this list (general, special class and automotive) along with three class types of mechanic trades (diesel, motor and motorcycle).

While there might still be some specialist jobs that are hard to fill, generally the downturn in the mining and petroleum industries are in the best environment for years in terms of recruiting skilled workers as layoffs, wage freezes and salary cuts become common place.

However, cash-strapped state governments have also been advancing plans to privatise electricity-related assets for some time now.

Of the potential bidders, China's SGC already has an interest in Victoria's transmission and distribution network plus is tipped to be among the most likely buyers for New South Wales' poles and wires network.

There have also been thousands of layoffs in this sector across both states, including from the likes of Ausgrid, TransGrid, NorthWestern Energy and Essential Energy.

An FTA concern which accompanies the 457 changes is the introduction of Investment Facilitation Arrangements which unions fear will be used to lower the incomes of Chinese workers under the scheme to below "the effective minimum wage of 457 visa workers granted under any similar projects".

There are also investor state dispute settlement clauses in the FTA deal which has triggered litigation fears.

"Let's say China State Grid was to bring in Chinese workers and the state government legislated to keep power prices down or to provide more training opportunities for Australian apprentices - it will be acceptable for Chinese companies to sue that state government to a trade commission under the terms of the agreement," a union source said.

The FTA still needs to be ratified by parliament with a letter signed by the national secretaries of eight big Australian trade unions asking the Labor Party to oppose it and "either succeed in significantly improving the agreement or block it entirely".

A big multi-union campaign is also in the works with industrial action under consideration.