Let's define Biosafety Level 4 (BSL-4) directly from the CDC doc - here (this doc includes very thorough definitions for each level of biosafety, a bit lengthy but worth understanding the differences): http://www.cdc.gov/biosafety/publications/bmbl5/bmbl5_sect_iv.pdf
Agents with a close or identical antigenic relationship to agents requiring BSL-4 containment must be handled at
this level until sufficient data are obtained either to confirm continued work at this
level, or re-designate the level.
As far as I know they have not downgraded the level for Ebola... so. There you go.
Level for Ebola has not been downgraded. But cdc guidelines for health care workers do not specify level 4 protective measures.
Dallas hospital does not have level 4 containment unit, like the one in Nebraska and Emory.
But CDC thinks regular hospitals without level 4 containment units should be fine treating Ebola patients.
Oops.