Collections codes are routinely tagged in the Plazi workflow that leads to 29K datasets, that is publications, in GBIF. They are also available in the materials citations aka ocurrences eg https://www.gbif.org/occurrence/2608702029 extracted from a publications: https://doi.org/10.11646/zootaxa.4407.1.2 and the respective taxonomic treatment. http://tb.plazi.org/GgServer/html/676A87E0FFA3B14D2392FD6C47540BD1 , and the collection code is annotated with the respective identifier http://biocol.org/urn:lsid:biocol.org:col:34871
This workflow existed before the the GRSciol broke down, and now that GBIF resumes this service, the identifiers even resolve.
Together with CETAF EJT a guideline exists on how to publish materials citation so that this extraction is more efficient. https://doi.org/10.5852/ejt.2019.586
Unfortunately the collection codes have not been included because the publishers, editors, authors, scientists are very far away from realizing this potential, and the focus has been on suggesting, that materials citations should be published in a standardized way to make this data type digitally accessible knowledge. Also a potential to find out how often specimen are being used - what has been mentioned above.
In the case of GBIF, it is now possible to go from a collection code to an “occurrence” aka materialsciation, to the taxonomic treatment, to the respective publication. It also allows increasingly, based on scholarly published data, to know who collected which specimen from a collection and many other thing, all in the respective data in the submitted record.