Speedover60,
If the Learjet that you have been flying is, under EASA, considered/classified as a Multicrew aircraft, then your experience on the Learjet will be taken in consideration towards the necessary 500 hrs multicrew needed for the issue of the ATPL License.
Not sure, but I believe that ALL Lear's are, under EASA, classified as a Multi pilot aircraft. For instance, some Cessna Citationīs are classified as Single pilot aircraft.
It is better if you check with the authority that issued your EASA CPL.