I suspect still not strictly true.
For holders of non easa licences ( not yet converted) it lifts the vfr limits and on top restriction any where and can be used any where with the consent of the national authority.
Increased VFR limits and VFR on top for non-EASA licences does not mean the IMC rating is valid outside of UK airspace and CI. The CAA alter your PPL privileges, and these are applicable worldwide.
Legally, the IMC rating can be used outside of UK airspace with the consent of the national authority, but in practical terms no other country has given that consent or is likely to do so.
(CI & IoM excepted)