One of the biggest fears about the tax overhaul bill in Congress already is showing signs of coming to fruition.

Critics of the Republican-sponsored plan say that a provision allowing companies to bring profits stored overseas back home at a one-time reduced tax rate wouldn't foster economic growth.

Instead, they argue, companies will use the windfall to reward investors with share buybacks and dividends. Democrats are using a handful of company buyback announcements to bolster their case.

"These companies, I'd say to President Trump and my Republican colleagues, are not announcing new investments or wage increases like Republicans promised they would," Sen. Chuck Schumer, D-N.Y., said on the Senate floor Thursday. "They're announcing stock repurchasing programs that benefit their wealthy investors."

Indeed, T-Mobile, Home Depot, Bank of America and Mastercard all announced significant repurchase intentions this week. Home Depot led the way with a $15 billion buyback after it raised its long-term sales target.

While the recent spate of buyback announcements is a small sample size, it brings back memories of the last time Congress tried to bring back cash overseas through a tax holiday.

In 2004, companies were allowed to bring their profits back home at a tax rate of 5.25 percent. But rather than pump that money into the economy, most of it went to shareholders, with some of the biggest recipients actually cutting employment in subsequent years.

Share buybacks have been on the decline in recent quarters, and likely grew less than 5 percent in the third quarter, according to Howard Silverblatt, senior index analyst at S&P Dow Jones Indices.

However, Silverblatt said buybacks could "increase substantially" should Congress approve the repatriation plan. The record of $172 billion in the third quarter of 2007 could be in play. By contrast, the current quarter is tracking for about $130 billion.

As for dividends, the third quarter is on pace to set a new record of $105.4 billion for companies. Silverblatt expects that record to fall in the fourth quarter, which is tracking for $107.4 billion.

However, he sees the balance of the repatriation windfall going to buybacks, which investors understand to be temporary, than dividends, which are harder to rescind.

The tax reform package overall is expected to provide a boost to earnings in the 14 percent range, according to Bank of America Merrill Lynch projections. The firm expects buybacks to account for about 16 percent of a total $19 per share benefit to the S&P 500.

Republicans backing the tax overhaul measure maintain that the repatriation, which would affect the $2.5 trillion or so of profits stowed overseas, will bring growth through investment of dormant money.

In fact, Gary Cohn, director of the White House's National Economic Council, has said that even if companies use the repatriation windfall to reward shareholders, that still will be better than allowing it to sit fallow abroad.

"If that's our worst-case scenario, that companies repatriate their money, and they use it for share buybacks and dividends, what happens? They buy back shares, they issue dividends. They pay the repatriation tax. We get another 20 percent tax on capital gains or dividends," Cohn told CNBC in October. "And then the people that get that money back do what? They reinvest it back in the economy in new investments and new capital."

WATCH: Senate hikes proposed tax rate for repatriated cash.