I tend to agree with Ken. I know of a few taximen who got very expensive shocks as what they call "loading" negated any perceived benefit of NCD protection. They don't disclose how loading is calculated as it's done on a "case by case basis" but it certainly seems to be adjusted to eliminate any NCD protection benefit that may otherwise have applied.
That said, I still pay it putting it down to prudence rather than lunacy. I just renewed with FBD via Taxifair and was charged €148.46 for NCD protection, total premium €1,437.20 (including Government levy and Insurance Compensation Fund of 5% which equates to €68.44) + €65 broker fee.