"have probably started" is correct and can be used in written English.
You can use it to express a hypothesis about an action that has possibly began. Example: The birds have probably started their migration south for the winter.
The reforms started by Mr. Manmohan Singh in 1990, however, could have probably started in 1980.
"When he got behind, I think even a year ago he would have probably started rushing a bit and, you know, panicking basically.
Wherever you are, Julia, in the Promised Land, in God's Kingdom, I'm sure you are finding happy hunting grounds along with Escoffier and have probably started revising "The Guide Culinaire" with him.
"I think that the companies have probably started to understand that, from a public relations standpoint, they were doing their best to shoot themselves in the foot," said Dr. Mark A. Wainberg, past president of the International AIDS Society, a scientists' group.
I am aware I have now made myself sound incredibly old, so I should probably tell you that I am 30, rather than 60 as you have probably started to suspect.
The low-educated high-income Finnish men have probably started with physically demanding jobs, without the motivation and skills to maintain an ideal weight as do the higher educational groups.
The infection had probably started in one line, perhaps contaminated during insertion, and spread through his bloodstream to the others.
Whether the Eagles start negotiations with Vick midseason, with eight games left, or late in the season, the clock has probably started ticking.
South had cleverly concealed the club deuce, leaving West thinking that his partner had probably started with only two clubs but perhaps he had three.
Japan's population of 127m has probably started to shrink, and is forecast by the government to fall to 101m by 2050.
At the least, Carnival has probably started a successful spoiling tactic by preventing Royal Caribbean from obtaining the 75percentt of votes from P&O shareholders required for the deal to proceed, analysts said.
