Toulon are the only team that will not give opportunities to young promising players. Clermont gave opportunities to Fofana, Domingo and Parra and backed them getting rid of experienced Joubert, Emmanuelli and Mignoni as they all proved good enough and better. Toulouse gave opportunities to Maestri, Fickou ahead of internationals like Millo-Chluski and Jauzion and they proved good enough. If they are good enough, they will get chances so there is no problem.
And if a player from the big club fails to break through or kick on, then they normally take a step down to a side like Castres who have established themselves as the dumping ground for that type of player with various other teams doing so.
There are 14 teams in the Top 14. And contrary to some people's belief, not all the league is full of Toulon's. 7 or 8 French starters in 14 teams on a weekend is still easily more places and chances available to that of Ireland with 4 teams with about 11 or 12 Irish starters each, and with 7 H Cup teams it is still more French players getting Heineken Cup chances.
Add to that Ireland congests their talent pool into 3 teams, in France somebody like James Downey or Mike Ross after struggling to breakthrough would have got more opportunity there dropping down to a lower side like Brive as opposed to having the leave the country and being lost as a potential Ireland selection.
So I really don't buy the "French teams are blocking French players". Just one team really does that as they hate internationals playing for them and have a side built around the Tri Nations and England players of about 2007. If they are good enough they will get chances at top clubs like Domingo, Fofana or Fickou have done. If not, then there are chances at mid table like Perpignan or lower league like Brive playing at a top level, as opposed to Ireland where there is just Connacht to drop down to if they fail to breakthrough.
This is just a poor excuse for France playing crap used by Saint-Andre. They have more players than the Celts and better resources in their league than the Celts and are underachieving behind them.