There's no supported/exposed way to retrieve the information from the tag reference tracker, but like most things in Ignition, it's still possible.
I would recommend doing this on the gateway, but if you've got a gateway context already, then something like this:
from com.inductiveautomation.ignition.common.tags.config.model import TagReferenceQuery
from com.inductiveautomation.ignition.common.tags.paths import BasicTagPath
# @param activeSubscriptions True, only return references from current subscriptions to tag. False, returns all other stored references.
# @param activeSince References where the most recent activity occurred before [activeSince] will be filtered from results. 0, to ignore and return all references.
query = TagReferenceQuery(
BasicTagPath("default", "path/to/tag".split("/")),
False, #activeSubscriptions
0 #activeSince
)
references = context.tagManager.getTagProvider("default").getTagReferences(query).get()