This would be more valuable IMO if in addition to the type, we had a reference to the K8s object

Agree , as there might be multiple resources for a crd, In future, for ex, we could support multiple egress ips,
Something like below will be more explanatory and respectively for other resources

ROUTE                    TYPE                  K8s OBJECT REFERENCE
172.18.0.3/32            EgressIP           Egress: egress-1

nit: I would add a Service prefix to these

The ability to provide a reference to the K8s object will require a different data structure here.
Personally, I would go with something like this:

type RouteMetadata struct {
        Type RouteType
        K8sObjRef string
}

routes map[bgp.Route]RouteMetadata

1. you can easily get a set of desired routes with sets.KeySet(c.routes), requiring only minimal changes in reconcileBGPAdvertisements
2. the handler will transform the data (as it already does) and filter routes if needed (based on type)