Conditional Perfect Progressive
The Spanish Perfect Conditional tense can also be progressive and express hypothetical situations that may have been happening in the past, seen as continuous possible actions: "something that would have (not) been happening". For example:
Yo habría estado saltando de alegría si eso me hubiera pasado a mí.
I would have been bursting with joy if that had happened to me.
Si yo fuera él, habría estado planeando mi huida.
If I were him, I would have been planning my escape.
¿Qué habrían estado haciendo esos chicos tan tarde en la calle?
[I wonder] what would those boys have been doing outside so late [at night]?