It’s easier to get a camel through the eye of a needle than to get some tech departments that support Research in Motion’s (RIMM) BlackBerry to change gears and support Apple’s (AAPL) iPhone.

But that’s starting to change, according to a report to clients issued Thursday by Merrill Lynch’s (BAC) Scott Craig.

Drawing on a survey of more than 200 information technology managers in enterprises with a total IT budget of at least $4 billion, Craig finds:

• The iPhone is making progress. 19% of respondents are using it in their organization in one form or another. Within this group, the iPhone has a 10% share and that share is expected to double next year.
• Resistance is beginning to melt. 11% of respondents expect to test and/or deploy iPhone over the next year, bringing the total number of respondents that should be using the iPhone in their enterprise in one year to about 30%
• Most IT departments are still holding out. 58% do not support or plan to support the iPhone. Reasons given: current smart phone strategy is sufficient (34%), cost of device/plan is too high (27%), and AT&T carrier lock-in (14%). See pie chart below the fold.

Below: More fun facts from the survey.

When asked, “Does your company support or plan to support iPhone?”

• Smaller companies (1-5K employees) have adopted the iPhone in their organization faster than larger companies, although not by much
• 4 respondents with employees more than 100K have adopted iPhone in all of their organization;
• U.S. companies have adopted faster than international companies;
• Government market has the least adoption and planned adoption; and
• Respondents in Computer Hardware industry showed the most adoption, with 25% indicated that the entire organization has adopted.

When asked, “Of the companies who adopted the phone, what percentage of your smart phone installed base is iPhone?” and “What about in the next 12 months?”

• U.S. companies have a larger installed base than international and were more aggressive about future adoption.

When asked, “For those who are not supporting iPhone, what are the reasons?”

• Larger organizations had more security concerns and issues with AT&T;
• The lower the overall IT budget, the more issues with cost of phone and service;
• International users had bigger issues with the actual cost of device; and
• Government have largest issues with security.

[Follow Philip Elmer-DeWitt on Twitter @philiped]