Are pods and services able to talk to each other across different kubernetes namespaces?
When you create a namespace with the basic configuration, it does not prevent connectivity from other namespaces. You can connect to Services in other namespaces using the DNS:
For your information, if you are looking for how to restrict the networking, you may want to look into the network policy for more details. (https://kubernetes.io/docs/concepts/services-networking/network-policies/)