PLEASE NOTE – the use of the prehospital Canadian C-spine rule applies ONLY to MLPS and EWEMS who participated in the study trial. As such, this answer only applies to paramedics working in those Services. Infographic available here (link).
To clarify, the Canadian C-Spine Rule (CCR) does not state that C-spine collars should only be used on stable, alert patients.
The CCR is used to identify patients that may not require a C-Spine collar. As such, the inclusion criteria must be met and no exclusion criteria can be present. In the case you describe, an alert and oriented patient who meets all other inclusion criteria and has no exclusion criteria can have the rule applied to determine if a C-Spine collar is required.
An unconscious patient would be excluded from having this rule applied. As such and in all cases, the BLS Spinal Restriction motion standard is then applied to determine if a C-Spine collar is required.
Furthermore, manual C-spine management is used until a C-spine collar can be applied. C-spine collars are used to stabilize the spine so that your hands can be freed up to provide other care once applied.