[time-nuts] Do Rb's injection lock ?

[Kit Scally]

Group,

Recent postings have highlighted the pitfalls of (mostly) unwanted IL activity. 
I currently have 2 different Rb oscillators in close proximity to each other sharing a common SMPSU.
Are Rubidium (Cs and maser) oscillators prone to injection locking?  If so, what would the likely mechanism(s) be ?  
I've given this some initial analysis and can't see anything obvious.

Regards,

Kit
VK2LL