company has to fund this deficit. Because well, you have to gurantee the retires to continue to receive their pension. If pension fund has surplus, then the company can do things with this surplus.
Pension actuaries advise the company what to do with their pension funds (by auditing the perfomance), how to set up pension funds and look at the retirement benefits/system for the company. But we don't actually manage these funds.
So it has nothing to do with insurance.
There are two branches in actuarial science. One is insurance and the other one is pension.