I'm a BE dev, and I can say (from my perspective) we work really well together.
It's a REST system and when a FE needs something me and my fellow BE teammates do all we can to give them that something.
During development they use moc's for the payloads that we're not ready to give them. When we build things FOR them all members are happy.
A good rule is to have the teams come to an agreement on the data that they need to show the user. Then have the BE team build out a rough payload.
Paired programming on features is always good.
Myself personally. I have a simple thing to keep in mind. FE keeps the customer happy, I keep FE happy, ops keeps us all happy. As long as BE remember they are there for the FE, everything flows smooth.