EgressIPs are not assigned to nodes following node scale down / scale up operation. The worker nodes are AWS m6a.16xlarge EC2 instances which can host up to 49 EgressIPs per node.
Annotations:        cloud.network.openshift.io/egress-ipconfig:
                      [{"interface":"eni-xxxx","ifaddr":{"ipv4":"10.x.x.0/18"},"capacity":{"ipv4":49,"ipv6":50}}]

    EgressIPs with OVN-Kubernetes

1. Create a worker machineset using m6a.16xlarge instance type     
2. Create 76 eips

for n in $(seq 5 80); do                                                                 
cat <<EOF |oc apply -f -
apiVersion: k8s.ovn.org/v1
kind: EgressIP
metadata:
  name: egress-10.0.40.${n}
spec:
  egressIPs:
  - 10.0.40.$n
  namespaceSelector:
    matchLabels:
      env: eip
EOF
done                                                                                     

3. Scale down the machineset to 0, and scale up to the previous number of instances 
     

 1. For a while there are cloudprivateipconfigs in "CloudResponsePending" state, but eventually most succeed:

$ oc get cloudprivateipconfigs -o yaml|yq '.items[].status.conditions[].reason'|sort|uniq -c 76 CloudResponseSucces

2. However 3 egressips remain unassigned

$ oc get eip --no-headers|awk '$3 == "" {print}'
egress-10.0.40.10   10.0.40.10                                                  
egress-10.0.40.13   10.0.40.13                                                  
egress-10.0.40.15   10.0.40.15

3. cloud-config-controller hits context deadline exceeded for 40.15, which is not assigned (see above):

$ oc logs -n openshift-cloud-network-config-controller deploy/cloud-network-config-controller |grep 40.15

I1206 13:20:18.154263       1 controller.go:182] Assigning key: 10.0.40.15 to cloud-private-ip-config workqueue
I1206 13:20:18.240415       1 controller.go:182] Assigning key: ip-10-0-44-127.eu-central-1.compute.internal to node workqueue
I1206 13:20:20.695067       1 cloudprivateipconfig_controller.go:439] Added IP address to node: "ip-10-0-32-145.eu-central-1.compute.internal" for CloudPrivateIPConfig: "10.0.40.15"
I1206 13:20:22.342670       1 controller.go:160] Dropping key '10.0.40.15' from the cloud-private-ip-config workqueue
E1206 13:20:49.140656       1 controller.go:165] error syncing '10.0.40.15': Get "https://api-int.bverschu.emea.aws.cee.support:6443/apis/cloud.network.openshift.io/v1/cloudprivateipconfigs/10.0.40.15": context deadline exceeded, requeuing in cloud-private-ip-config workqueue
E1206 13:21:10.340015       1 controller.go:165] error syncing '10.0.40.68': error updating CloudPrivateIPConfig: "10.0.40.68", err: Put "https://api-int.bverschu.emea.aws.cee.support:6443/apis/cloud.network.openshift.io/v1/cloudprivateipconfigs/10.0.40.68/status": context deadline exceeded, requeuing in cloud-private-ip-config workqueue
E1206 13:21:14.539786       1 controller.go:165] error syncing '10.0.40.15': Get "https://api-int.bverschu.emea.aws.cee.support:6443/apis/cloud.network.openshift.io/v1/cloudprivateipconfigs/10.0.40.15": context deadline exceeded, requeuing in cloud-private-ip-config workqueue
I1206 13:21:39.339112       1 controller.go:160] Dropping key '10.0.40.15' from the cloud-private-ip-config workqueue   

All EgressIPs are assigned to nodes.