I haven't watched these markets in a long time but most of my experience was with the US 10yr. I was down on the floor quoting the activity in the 10yr futures and options pits so will throw in a bit of 2 cents in here. First, with the short end of the US curve there were very few locals, those locals that actually did trade it were probably 90% spreaders and calendar roll traders. These guys would stand in the 2yr and 5yr pits (along with their screens) and just trade the TUF, FIT, and TUT's all day. Trying to pick up ticks here and there. Further out the curve in the 10yr and 30yr you would get a few spreaders (NOB traders) and then the outright guys. Majority of the volume in the short end of the curve is between off floor traders, just too much volume and smaller volatilities for the big locals to make money without HUGE positions. At least in the US market the majority of the cash volumes done are in the 2yr and 5yr on a dollar basis. A lot of this is done vs. swaps as well. So lots of big trades basically crossed between desks in the various banks. Eurodollars the same story, all swap and commerical paper desks laying off various cash and OTC traders basically against each other. Why else do you think the short end instruments throughout the world are going to half and quarter ticks. Plain and simple smaller transaction fee and price of liquidity to pay for their hedges, and wider OTC markets equals huge bank earnings.
As for the big position guys maybe 3, 4, or 5 years ago they were able to move the US 10yr and actually push the market a bit sometimes. Mortgage hedging activity was very small because spreads vs. Treasuries were pretty narrow and not volatile. Brumfield used to fill the whole order book and also have his guys standing in the pit so basically knew the whole order flow (along with using some counterparty software) and if it was a local dominated market or paper and trade that against his levels. Big moves during that period when volatility was under 4% would be a 10 full tick range, maybe 20 on really busy days. Volume was high though so he could trade huge sizes and bully the market. Now that can't happen. Mortgage hedging activity into the 10yr futures is enormous to say the least, at least 1 million futures every day maybe closer to 1.5 and another 250,000 plus options every day tells the story. Big locals CAN NOT push this market anymore at least in the US. The volatility is so large they can go back to only trading 1000 lots or even less and make the same amount of money. Their job is to be able to come back the next day not blow out, when you trade the banks money you can mess around with hitting or lifting 5000 lot bids and offers.