El present perfect continuous con un verbo modal probablemente no se usa mucho, ni en español ni en inglés. Sin embargo frases de este tipo son posibles.

Ella ha podido estar durmiendo cuando la has llamado esta mañana, por eso no ha respondido.

Sea como sea, la formación sigue las mismas reglas que ya conocemos. Vea también el capítulo 8.3.5.

ejemplos
present perfect del verbo modal + verbo pleno + sufijo -ing = present perfect continuous
he might have been do ing he might have been doing
she could have been writ(e) ing she could have been writing
we have to have been jump ing we have to have been jumping
they should have been sell ing they should have been selling
you need to have been study ing you need to have been studying
I ought to have been watch ing I ought to have been watching