For OSPF reference bw, I don't know any CLI command to check. For this parameter (And a lot of other global parameters), you have not option but to TRUST what has been configured on the router.
Even if we have some commands like "show ospf overview" which provides the reference bw. What additional value is it adding on top of the config? Fairely speaking, we are NOT expecting any difference between what has been configured and what is applied
We all know how to do the math here: cost = reference BW / BW
You can do "show ospf interface extensive" and verify the cost on the link
Juniper does not have an 'ospf' operational command that will tell you operationally the 'Reference bandwidth', basically you would need to check the configured value using "user@switch> show configuration ospf | display set | match reference" if there is anything configured that's the reference bandwidth, if not, the default value is 100mbps
By default, OSPF assigns a default cost metric of 1 to any link faster than 100 Mbps, and a default cost metric of 0 to the loopback interface (lo0). No bandwidth is associated with the loopback interface.