PADI '08 Digital Instructor Manual:
Dive Depth Limits
The maximum depth for any Adven-
ture Dive is 30 metres/100 feet. For
12-14 year olds, the maximum depth
for any Adventure Dive is 21 me-
tres/70 feet. For 10-11 year olds the
maximum depth is 12 metres/40 feet.
PADI only has Standards for training dives; for non-training dives PADI "only" makes recommendations.
Once a diver reaches age 15, the training dive Standard for the diver's level of certification is the "basic" recommendation depth, but "experience" is another term used in the recommendations.
Since a 15 year old with Jr. AOW is not required to do anything other than "pay" for an AOW card, I have run into many 20-somethings that still only have a Jr. AOW card and an operator limiting depth to 70 feet for divers 15 and up is pretty rare, even just OW certified divers.
Jr. AOW and the Deep Adventure Dive are not allowed for 10-11 year olds; under 12 the recommendation is always no deeper than 40 feet.
If a 12-14 year old diver has completed Jr. AOW or the Deep Adventure Dive, the PADI recommendation is not to go deeper than 70 feet; 60 feet for Jr. OW divers without the Deep Adventure Dive.
On a Jr. AOW Diver's 15th b-day, the recommendation drops to no deeper than 100 feet; even though no training below 70 feet has ever happened.
V&B is the insurance company "in bed" with PADI. It is possible that V&B policies may limit PADI Pro's from exceeding the PADI recommendations.
From my previous research, I find no indication any other dive boat insurer limits certified divers with regards to depth, as long as the "dive leader" has training appropriate for the dive.